diff --git a/go-services/inventory-go/od.go b/go-services/inventory-go/od.go
new file mode 100644
index 00000000..56d93a44
--- /dev/null
+++ b/go-services/inventory-go/od.go
@@ -0,0 +1,562 @@
+package main
+
+import "math"
+
+// od.go computes the Mag-Tools "OD" (over-damage vs best retail) rating for
+// melee/missile/wand weapons, ported from UtilityBelt's
+// Lib/ItemInfoHelper/{WeaponMods,MiscCalcs,Dictionaries}.cs and
+// Tools/ItemInfo.cs (CalcMeleeDamage / CalcMissileDamage / the OD display
+// lines ~631-647). See docs/superpowers/specs/2026-07-15-weapon-od-rating-design.md.
+
+// bestKey mirrors the (Skill, Mastery, MultiStrike, WieldReq) DataTable.Select
+// key UB uses for an EXACT match lookup — no nearest-tier rounding.
+type bestKey struct {
+	skill       int
+	mastery     int
+	multiStrike int
+	wieldReq    int
+}
+
+// bestValue mirrors the trailing DataTable columns:
+// (MaxDmg, MaxVar, MaxDmgMod, MaxElementalDmgBonus, MaxElementalDmgVsMonsters).
+type bestValue struct {
+	maxDmg       float64
+	maxVar       float64
+	maxDmgMod    float64
+	maxElemBonus float64
+	maxElemVsMon float64
+}
+
+// bestValues is transcribed row-for-row from
+// UtilityBelt/UtilityBelt/Lib/ItemInfoHelper/WeaponMods.cs BestValuesDatatable.GetTable().
+// Column order in the source Rows.Add is:
+// (Skill, Mastery, MultiStrike, WieldReq, MaxDmg, MaxVar, MaxDmgMod, MaxElementalDmgBonus, MaxElementalDmgVsMonsters)
+// — omitted trailing columns default to 0. 301 rows total (matches
+// `grep -c "table.Rows.Add" WeaponMods.cs`).
+var bestValues = map[bestKey]bestValue{
+	// heavyweaponry (skill 44) http://acpedia.org/wiki/Heavy_Weaponry
+	// axe
+	{44, 3, 0, 0}:   {26, .90, 0, 0, 0},
+	{44, 3, 0, 250}: {33, .90, 0, 0, 0},
+	{44, 3, 0, 300}: {40, .90, 0, 0, 0},
+	{44, 3, 0, 325}: {47, .90, 0, 0, 0},
+	{44, 3, 0, 350}: {54, .90, 0, 0, 0},
+	{44, 3, 0, 370}: {61, .90, 0, 0, 0},
+	{44, 3, 0, 400}: {69, .90, 0, 0, 0},
+	{44, 3, 0, 420}: {71, .90, 0, 0, 0},
+	{44, 3, 0, 430}: {74, .90, 0, 0, 0},
+	// dagger
+	{44, 6, 0, 0}:   {24, .47, 0, 0, 0},
+	{44, 6, 0, 250}: {31, .47, 0, 0, 0},
+	{44, 6, 0, 300}: {38, .47, 0, 0, 0},
+	{44, 6, 0, 325}: {45, .47, 0, 0, 0},
+	{44, 6, 0, 350}: {51, .47, 0, 0, 0},
+	{44, 6, 0, 370}: {58, .47, 0, 0, 0},
+	{44, 6, 0, 400}: {65, .47, 0, 0, 0},
+	{44, 6, 0, 420}: {68, .47, 0, 0, 0},
+	{44, 6, 0, 430}: {71, .47, 0, 0, 0},
+	// msdagger
+	{44, 6, 1, 0}:   {13, .40, 0, 0, 0},
+	{44, 6, 1, 250}: {16, .40, 0, 0, 0},
+	{44, 6, 1, 300}: {20, .40, 0, 0, 0},
+	{44, 6, 1, 325}: {23, .40, 0, 0, 0},
+	{44, 6, 1, 350}: {26, .40, 0, 0, 0},
+	{44, 6, 1, 370}: {30, .40, 0, 0, 0},
+	{44, 6, 1, 400}: {33, .40, 0, 0, 0},
+	{44, 6, 1, 420}: {36, .40, 0, 0, 0},
+	{44, 6, 1, 430}: {38, .40, 0, 0, 0},
+	// mace
+	{44, 4, 0, 0}:   {22, .30, 0, 0, 0},
+	{44, 4, 0, 250}: {29, .30, 0, 0, 0},
+	{44, 4, 0, 300}: {36, .30, 0, 0, 0},
+	{44, 4, 0, 325}: {43, .30, 0, 0, 0},
+	{44, 4, 0, 350}: {49, .30, 0, 0, 0},
+	{44, 4, 0, 370}: {56, .30, 0, 0, 0},
+	{44, 4, 0, 400}: {63, .30, 0, 0, 0},
+	{44, 4, 0, 420}: {66, .30, 0, 0, 0},
+	{44, 4, 0, 430}: {69, .30, 0, 0, 0},
+	// spear
+	{44, 5, 0, 0}:   {25, .59, 0, 0, 0},
+	{44, 5, 0, 250}: {32, .59, 0, 0, 0},
+	{44, 5, 0, 300}: {39, .59, 0, 0, 0},
+	{44, 5, 0, 325}: {46, .59, 0, 0, 0},
+	{44, 5, 0, 350}: {58, .59, 0, 0, 0},
+	{44, 5, 0, 370}: {59, .59, 0, 0, 0},
+	{44, 5, 0, 400}: {66, .59, 0, 0, 0},
+	{44, 5, 0, 420}: {69, .59, 0, 0, 0},
+	{44, 5, 0, 430}: {72, .59, 0, 0, 0},
+	// sword
+	{44, 2, 0, 0}:   {24, .47, 0, 0, 0},
+	{44, 2, 0, 250}: {31, .47, 0, 0, 0},
+	{44, 2, 0, 300}: {38, .47, 0, 0, 0},
+	{44, 2, 0, 325}: {45, .47, 0, 0, 0},
+	{44, 2, 0, 350}: {51, .47, 0, 0, 0},
+	{44, 2, 0, 370}: {58, .47, 0, 0, 0},
+	{44, 2, 0, 400}: {65, .47, 0, 0, 0},
+	{44, 2, 0, 420}: {68, .47, 0, 0, 0},
+	{44, 2, 0, 430}: {71, .47, 0, 0, 0},
+	// mssword
+	{44, 2, 1, 0}:   {13, .40, 0, 0, 0},
+	{44, 2, 1, 250}: {16, .40, 0, 0, 0},
+	{44, 2, 1, 300}: {20, .40, 0, 0, 0},
+	{44, 2, 1, 325}: {23, .40, 0, 0, 0},
+	{44, 2, 1, 350}: {26, .40, 0, 0, 0},
+	{44, 2, 1, 370}: {30, .40, 0, 0, 0},
+	{44, 2, 1, 400}: {33, .40, 0, 0, 0},
+	{44, 2, 1, 420}: {36, .40, 0, 0, 0},
+	{44, 2, 1, 430}: {38, .40, 0, 0, 0},
+	// staff
+	{44, 7, 0, 0}:   {23, .38, 0, 0, 0},
+	{44, 7, 0, 250}: {30, .38, 0, 0, 0},
+	{44, 7, 0, 300}: {36, .38, 0, 0, 0},
+	{44, 7, 0, 325}: {43, .38, 0, 0, 0},
+	{44, 7, 0, 350}: {50, .38, 0, 0, 0},
+	{44, 7, 0, 370}: {56, .38, 0, 0, 0},
+	{44, 7, 0, 400}: {63, .38, 0, 0, 0},
+	{44, 7, 0, 420}: {66, .38, 0, 0, 0},
+	{44, 7, 0, 430}: {70, .38, 0, 0, 0},
+	// ua
+	{44, 1, 0, 0}:   {20, .44, 0, 0, 0},
+	{44, 1, 0, 250}: {26, .44, 0, 0, 0},
+	{44, 1, 0, 300}: {31, .44, 0, 0, 0},
+	{44, 1, 0, 325}: {37, .44, 0, 0, 0},
+	{44, 1, 0, 350}: {43, .44, 0, 0, 0},
+	{44, 1, 0, 370}: {48, .44, 0, 0, 0},
+	{44, 1, 0, 400}: {54, .44, 0, 0, 0},
+	{44, 1, 0, 420}: {56, .44, 0, 0, 0},
+	{44, 1, 0, 430}: {59, .44, 0, 0, 0},
+
+	// light weaponry (skill 45) http://acpedia.org/wiki/Light_Weaponry
+	// axe
+	{45, 3, 0, 0}:   {22, .80, 0, 0, 0},
+	{45, 3, 0, 250}: {28, .80, 0, 0, 0},
+	{45, 3, 0, 300}: {33, .80, 0, 0, 0},
+	{45, 3, 0, 325}: {39, .80, 0, 0, 0},
+	{45, 3, 0, 350}: {44, .80, 0, 0, 0},
+	{45, 3, 0, 370}: {50, .80, 0, 0, 0},
+	{45, 3, 0, 400}: {55, .80, 0, 0, 0},
+	{45, 3, 0, 420}: {57, .80, 0, 0, 0},
+	{45, 3, 0, 430}: {61, .80, 0, 0, 0},
+	// dagger
+	{45, 6, 0, 0}:   {18, .42, 0, 0, 0},
+	{45, 6, 0, 250}: {24, .42, 0, 0, 0},
+	{45, 6, 0, 300}: {29, .42, 0, 0, 0},
+	{45, 6, 0, 325}: {35, .42, 0, 0, 0},
+	{45, 6, 0, 350}: {40, .42, 0, 0, 0},
+	{45, 6, 0, 370}: {46, .42, 0, 0, 0},
+	{45, 6, 0, 400}: {51, .42, 0, 0, 0},
+	{45, 6, 0, 420}: {54, .42, 0, 0, 0},
+	{45, 6, 0, 430}: {58, .42, 0, 0, 0},
+	// msdagger
+	{45, 6, 1, 0}:   {7, .24, 0, 0, 0},
+	{45, 6, 1, 250}: {11, .24, 0, 0, 0},
+	{45, 6, 1, 300}: {13, .24, 0, 0, 0},
+	{45, 6, 1, 325}: {16, .24, 0, 0, 0},
+	{45, 6, 1, 350}: {18, .24, 0, 0, 0},
+	{45, 6, 1, 370}: {21, .24, 0, 0, 0},
+	{45, 6, 1, 400}: {24, .24, 0, 0, 0},
+	{45, 6, 1, 420}: {27, .24, 0, 0, 0},
+	{45, 6, 1, 430}: {28, .24, 0, 0, 0},
+	// mace
+	{45, 4, 0, 0}:   {19, .23, 0, 0, 0},
+	{45, 4, 0, 250}: {24, .23, 0, 0, 0},
+	{45, 4, 0, 300}: {29, .23, 0, 0, 0},
+	{45, 4, 0, 325}: {35, .23, 0, 0, 0},
+	{45, 4, 0, 350}: {40, .23, 0, 0, 0},
+	{45, 4, 0, 370}: {45, .23, 0, 0, 0},
+	{45, 4, 0, 400}: {50, .23, 0, 0, 0},
+	{45, 4, 0, 420}: {53, .23, 0, 0, 0},
+	{45, 4, 0, 430}: {57, .23, 0, 0, 0},
+	// spear
+	{45, 5, 0, 0}:   {21, .65, 0, 0, 0},
+	{45, 5, 0, 250}: {26, .65, 0, 0, 0},
+	{45, 5, 0, 300}: {32, .65, 0, 0, 0},
+	{45, 5, 0, 325}: {37, .65, 0, 0, 0},
+	{45, 5, 0, 350}: {42, .65, 0, 0, 0},
+	{45, 5, 0, 370}: {48, .65, 0, 0, 0},
+	{45, 5, 0, 400}: {53, .65, 0, 0, 0},
+	{45, 5, 0, 420}: {57, .65, 0, 0, 0},
+	{45, 5, 0, 430}: {60, .65, 0, 0, 0},
+	// sword
+	{45, 2, 0, 0}:   {20, .42, 0, 0, 0},
+	{45, 2, 0, 250}: {25, .42, 0, 0, 0},
+	{45, 2, 0, 300}: {31, .42, 0, 0, 0},
+	{45, 2, 0, 325}: {36, .42, 0, 0, 0},
+	{45, 2, 0, 350}: {41, .42, 0, 0, 0},
+	{45, 2, 0, 370}: {47, .42, 0, 0, 0},
+	{45, 2, 0, 400}: {52, .42, 0, 0, 0},
+	{45, 2, 0, 420}: {55, .42, 0, 0, 0},
+	{45, 2, 0, 430}: {58, .42, 0, 0, 0},
+	// mssword
+	{45, 2, 1, 0}:   {7, .24, 0, 0, 0},
+	{45, 2, 1, 250}: {10, .24, 0, 0, 0},
+	{45, 2, 1, 300}: {13, .24, 0, 0, 0},
+	{45, 2, 1, 325}: {16, .24, 0, 0, 0},
+	{45, 2, 1, 350}: {18, .24, 0, 0, 0},
+	{45, 2, 1, 370}: {21, .24, 0, 0, 0},
+	{45, 2, 1, 400}: {24, .24, 0, 0, 0},
+	{45, 2, 1, 420}: {25, .24, 0, 0, 0},
+	{45, 2, 1, 430}: {28, .24, 0, 0, 0},
+	// staff
+	{45, 7, 0, 0}:   {19, .325, 0, 0, 0},
+	{45, 7, 0, 250}: {24, .325, 0, 0, 0},
+	{45, 7, 0, 300}: {30, .325, 0, 0, 0},
+	{45, 7, 0, 325}: {35, .325, 0, 0, 0},
+	{45, 7, 0, 350}: {40, .325, 0, 0, 0},
+	{45, 7, 0, 370}: {46, .325, 0, 0, 0},
+	{45, 7, 0, 400}: {51, .325, 0, 0, 0},
+	{45, 7, 0, 420}: {54, .325, 0, 0, 0},
+	{45, 7, 0, 430}: {57, .325, 0, 0, 0},
+	// ua
+	{45, 1, 0, 0}:   {17, .43, 0, 0, 0},
+	{45, 1, 0, 250}: {23, .43, 0, 0, 0},
+	{45, 1, 0, 300}: {27, .43, 0, 0, 0},
+	{45, 1, 0, 325}: {31, .43, 0, 0, 0},
+	{45, 1, 0, 350}: {35, .43, 0, 0, 0},
+	{45, 1, 0, 370}: {40, .43, 0, 0, 0},
+	{45, 1, 0, 400}: {44, .43, 0, 0, 0},
+	{45, 1, 0, 420}: {46, .43, 0, 0, 0},
+	{45, 1, 0, 430}: {48, .43, 0, 0, 0},
+
+	// finesse weaponry (skill 46) http://acpedia.org/wiki/Finesse_Weaponry
+	// axe
+	{46, 3, 0, 0}:   {22, .80, 0, 0, 0},
+	{46, 3, 0, 250}: {28, .80, 0, 0, 0},
+	{46, 3, 0, 300}: {33, .80, 0, 0, 0},
+	{46, 3, 0, 325}: {39, .80, 0, 0, 0},
+	{46, 3, 0, 350}: {44, .80, 0, 0, 0},
+	{46, 3, 0, 370}: {50, .80, 0, 0, 0},
+	{46, 3, 0, 400}: {55, .80, 0, 0, 0},
+	{46, 3, 0, 420}: {57, .80, 0, 0, 0},
+	{46, 3, 0, 430}: {61, .80, 0, 0, 0},
+	// dagger
+	{46, 6, 0, 0}:   {18, .42, 0, 0, 0},
+	{46, 6, 0, 250}: {24, .42, 0, 0, 0},
+	{46, 6, 0, 300}: {29, .42, 0, 0, 0},
+	{46, 6, 0, 325}: {35, .42, 0, 0, 0},
+	{46, 6, 0, 350}: {40, .42, 0, 0, 0},
+	{46, 6, 0, 370}: {46, .42, 0, 0, 0},
+	{46, 6, 0, 400}: {51, .42, 0, 0, 0},
+	{46, 6, 0, 420}: {54, .42, 0, 0, 0},
+	{46, 6, 0, 430}: {58, .42, 0, 0, 0},
+	// msdagger
+	{46, 6, 1, 0}:   {7, .24, 0, 0, 0},
+	{46, 6, 1, 250}: {11, .24, 0, 0, 0},
+	{46, 6, 1, 300}: {13, .24, 0, 0, 0},
+	{46, 6, 1, 325}: {16, .24, 0, 0, 0},
+	{46, 6, 1, 350}: {18, .24, 0, 0, 0},
+	{46, 6, 1, 370}: {21, .24, 0, 0, 0},
+	{46, 6, 1, 400}: {24, .24, 0, 0, 0},
+	{46, 6, 1, 420}: {27, .24, 0, 0, 0},
+	{46, 6, 1, 430}: {28, .24, 0, 0, 0},
+	// mace
+	{46, 4, 0, 0}:   {19, .23, 0, 0, 0},
+	{46, 4, 0, 250}: {24, .23, 0, 0, 0},
+	{46, 4, 0, 300}: {29, .23, 0, 0, 0},
+	{46, 4, 0, 325}: {35, .23, 0, 0, 0},
+	{46, 4, 0, 350}: {40, .23, 0, 0, 0},
+	{46, 4, 0, 370}: {45, .23, 0, 0, 0},
+	{46, 4, 0, 400}: {50, .23, 0, 0, 0},
+	{46, 4, 0, 420}: {53, .23, 0, 0, 0},
+	{46, 4, 0, 430}: {57, .23, 0, 0, 0},
+	// spear
+	{46, 5, 0, 0}:   {21, .65, 0, 0, 0},
+	{46, 5, 0, 250}: {26, .65, 0, 0, 0},
+	{46, 5, 0, 300}: {32, .65, 0, 0, 0},
+	{46, 5, 0, 325}: {37, .65, 0, 0, 0},
+	{46, 5, 0, 350}: {42, .65, 0, 0, 0},
+	{46, 5, 0, 370}: {48, .65, 0, 0, 0},
+	{46, 5, 0, 400}: {53, .65, 0, 0, 0},
+	{46, 5, 0, 420}: {57, .65, 0, 0, 0},
+	{46, 5, 0, 430}: {60, .65, 0, 0, 0},
+	// sword
+	{46, 2, 0, 0}:   {20, .42, 0, 0, 0},
+	{46, 2, 0, 250}: {25, .42, 0, 0, 0},
+	{46, 2, 0, 300}: {31, .42, 0, 0, 0},
+	{46, 2, 0, 325}: {36, .42, 0, 0, 0},
+	{46, 2, 0, 350}: {41, .42, 0, 0, 0},
+	{46, 2, 0, 370}: {47, .42, 0, 0, 0},
+	{46, 2, 0, 400}: {52, .42, 0, 0, 0},
+	{46, 2, 0, 420}: {55, .42, 0, 0, 0},
+	{46, 2, 0, 430}: {58, .42, 0, 0, 0},
+	// mssword
+	{46, 2, 1, 0}:   {7, .24, 0, 0, 0},
+	{46, 2, 1, 250}: {10, .24, 0, 0, 0},
+	{46, 2, 1, 300}: {13, .24, 0, 0, 0},
+	{46, 2, 1, 325}: {16, .24, 0, 0, 0},
+	{46, 2, 1, 350}: {18, .24, 0, 0, 0},
+	{46, 2, 1, 370}: {21, .24, 0, 0, 0},
+	{46, 2, 1, 400}: {24, .24, 0, 0, 0},
+	{46, 2, 1, 420}: {25, .24, 0, 0, 0},
+	{46, 2, 1, 430}: {28, .24, 0, 0, 0},
+	// staff
+	{46, 7, 0, 0}:   {19, .325, 0, 0, 0},
+	{46, 7, 0, 250}: {24, .325, 0, 0, 0},
+	{46, 7, 0, 300}: {30, .325, 0, 0, 0},
+	{46, 7, 0, 325}: {35, .325, 0, 0, 0},
+	{46, 7, 0, 350}: {40, .325, 0, 0, 0},
+	{46, 7, 0, 370}: {46, .325, 0, 0, 0},
+	{46, 7, 0, 400}: {51, .325, 0, 0, 0},
+	{46, 7, 0, 420}: {54, .325, 0, 0, 0},
+	{46, 7, 0, 430}: {57, .325, 0, 0, 0},
+	// ua
+	{46, 1, 0, 0}:   {17, .43, 0, 0, 0},
+	{46, 1, 0, 250}: {23, .43, 0, 0, 0},
+	{46, 1, 0, 300}: {27, .43, 0, 0, 0},
+	{46, 1, 0, 325}: {31, .43, 0, 0, 0},
+	{46, 1, 0, 350}: {35, .43, 0, 0, 0},
+	{46, 1, 0, 370}: {40, .43, 0, 0, 0},
+	{46, 1, 0, 400}: {44, .43, 0, 0, 0},
+	{46, 1, 0, 420}: {46, .43, 0, 0, 0},
+	{46, 1, 0, 430}: {48, .43, 0, 0, 0},
+
+	// twohanded (skill 41) http://acpedia.org/wiki/Two_Handed_Weaponry
+	// cleaver
+	{41, 11, 1, 0}:   {13, .30, 0, 0, 0},
+	{41, 11, 1, 250}: {17, .30, 0, 0, 0},
+	{41, 11, 1, 300}: {22, .30, 0, 0, 0},
+	{41, 11, 1, 325}: {26, .30, 0, 0, 0},
+	{41, 11, 1, 350}: {30, .30, 0, 0, 0},
+	{41, 11, 1, 370}: {35, .30, 0, 0, 0},
+	{41, 11, 1, 400}: {39, .30, 0, 0, 0},
+	{41, 11, 1, 420}: {42, .30, 0, 0, 0},
+	{41, 11, 1, 430}: {45, .30, 0, 0, 0},
+	// spear
+	{41, 11, 0, 0}:   {14, .35, 0, 0, 0},
+	{41, 11, 0, 250}: {19, .35, 0, 0, 0},
+	{41, 11, 0, 300}: {24, .35, 0, 0, 0},
+	{41, 11, 0, 325}: {29, .35, 0, 0, 0},
+	{41, 11, 0, 350}: {33, .35, 0, 0, 0},
+	{41, 11, 0, 370}: {37, .35, 0, 0, 0},
+	{41, 11, 0, 400}: {42, .35, 0, 0, 0},
+	{41, 11, 0, 420}: {45, .35, 0, 0, 0},
+	{41, 11, 0, 430}: {48, .35, 0, 0, 0},
+
+	// missile (skill 47) http://acpedia.org/wiki/Missile_Weaponry/Bows
+	// bow (mastery 8)
+	{47, 8, 0, 0}:   {0, 0, 110, 0, 0},
+	{47, 8, 0, 250}: {0, 0, 120, 0, 0},
+	{47, 8, 0, 270}: {0, 0, 130, 0, 0},
+	{47, 8, 0, 290}: {0, 0, 140, 0, 0},
+	{47, 8, 0, 315}: {0, 0, 140, 5, 0},
+	{47, 8, 0, 335}: {0, 0, 140, 9, 0},
+	{47, 8, 0, 360}: {0, 0, 140, 16, 0},
+	{47, 8, 0, 375}: {0, 0, 140, 19, 0},
+	{47, 8, 0, 385}: {0, 0, 140, 22, 0},
+	// xbow (mastery 9)
+	{47, 9, 0, 0}:   {0, 0, 140, 0, 0},
+	{47, 9, 0, 250}: {0, 0, 150, 0, 0},
+	{47, 9, 0, 270}: {0, 0, 155, 0, 0},
+	{47, 9, 0, 290}: {0, 0, 165, 0, 0},
+	{47, 9, 0, 315}: {0, 0, 165, 5, 0},
+	{47, 9, 0, 335}: {0, 0, 165, 9, 0},
+	{47, 9, 0, 360}: {0, 0, 165, 16, 0},
+	{47, 9, 0, 375}: {0, 0, 165, 19, 0},
+	{47, 9, 0, 385}: {0, 0, 165, 22, 0},
+	// thrown (mastery 10)
+	{47, 10, 0, 0}:   {0, 0, 130, 0, 0},
+	{47, 10, 0, 250}: {0, 0, 140, 0, 0},
+	{47, 10, 0, 270}: {0, 0, 150, 0, 0},
+	{47, 10, 0, 290}: {0, 0, 160, 0, 0},
+	{47, 10, 0, 315}: {0, 0, 160, 5, 0},
+	{47, 10, 0, 335}: {0, 0, 160, 9, 0},
+	{47, 10, 0, 360}: {0, 0, 160, 16, 0},
+	{47, 10, 0, 375}: {0, 0, 160, 19, 0},
+	{47, 10, 0, 385}: {0, 0, 160, 22, 0},
+
+	// wands (skill 34 war / 43 void) http://acpedia.org/wiki/Magic_Casters
+	{34, 0, 0, 290}: {0, 0, 0, 0, 1.03},
+	{34, 0, 0, 315}: {0, 0, 0, 0, 1.06},
+	{34, 0, 0, 335}: {0, 0, 0, 0, 1.09},
+	{34, 0, 0, 360}: {0, 0, 0, 0, 1.13},
+	{34, 0, 0, 375}: {0, 0, 0, 0, 1.16},
+	{34, 0, 0, 385}: {0, 0, 0, 0, 1.18},
+
+	{43, 0, 0, 290}: {0, 0, 0, 0, 1.03},
+	{43, 0, 0, 315}: {0, 0, 0, 0, 1.06},
+	{43, 0, 0, 335}: {0, 0, 0, 0, 1.09},
+	{43, 0, 0, 360}: {0, 0, 0, 0, 1.13},
+	{43, 0, 0, 375}: {0, 0, 0, 0, 1.16},
+	{43, 0, 0, 385}: {0, 0, 0, 0, 1.18},
+	// void vr wand - not sure why this is different (mastery 12)
+	{43, 12, 0, 385}: {0, 0, 0, 0, 1.18},
+}
+
+// maxDamageSpellBonus is transcribed from UB Dictionaries.cs
+// LongValueKeySpellEffects entries keyed on LongValueKey_MaxDamage (218103842).
+var maxDamageSpellBonus = map[int]int{
+	1616: 20,  // Blood Drinker VI
+	2096: 22,  // Infected Caress
+	5183: 24,  // Incantation of Blood Drinker (post Feb-2013)
+	4395: 24,  // Incantation of Blood Drinker (post Feb-2013)
+	2598: 2,   // Minor Blood Thirst
+	2586: 4,   // Major Blood Thirst
+	4661: 7,   // Epic Blood Thirst
+	6089: 10,  // Legendary Blood Thirst
+	3688: 300, // Prodigal Blood Drinker
+}
+
+// elemVsMonSpellBonus is transcribed from UB Dictionaries.cs
+// DoubleValueKeySpellEffects entries keyed on DoubleValueKey_ElementalDamageVersusMonsters (152).
+var elemVsMonSpellBonus = map[int]float64{
+	3258: .06, // Spirit Drinker VI
+	3259: .07, // Infected Spirit Caress
+	5182: .08, // Incantation of Spirit Drinker (post Feb-2013)
+	4414: .08, // Incantation of Spirit Drinker (post Feb-2013)
+	3251: .01, // Minor Spirit Thirst
+	3250: .03, // Major Spirit Thirst
+	4670: .05, // Epic Spirit Thirst
+	6098: .07, // Legendary Spirit Thirst
+}
+
+// buffedMaxDamage mirrors GetBuffedIntValueKey(218103842): base value plus
+// bonus for each innate spell (raw["Spells"]), minus bonus for each active
+// spell (raw["ActiveSpells"]).
+func buffedMaxDamage(raw, iv map[string]any) int {
+	value := ivI(iv, "218103842", 0)
+	for _, id := range toIntList(raw["Spells"]) {
+		if b, ok := maxDamageSpellBonus[id]; ok {
+			value += b
+		}
+	}
+	for _, id := range toIntList(raw["ActiveSpells"]) {
+		if b, ok := maxDamageSpellBonus[id]; ok {
+			value -= b
+		}
+	}
+	return value
+}
+
+// buffedElemVsMon mirrors GetBuffedDoubleValueKey(152) using the same
+// innate-add / active-subtract semantics.
+func buffedElemVsMon(raw, dv map[string]any) float64 {
+	value := dvF(dv, "152", 0)
+	for _, id := range toIntList(raw["Spells"]) {
+		if b, ok := elemVsMonSpellBonus[id]; ok {
+			value += b
+		}
+	}
+	for _, id := range toIntList(raw["ActiveSpells"]) {
+		if b, ok := elemVsMonSpellBonus[id]; ok {
+			value -= b
+		}
+	}
+	return value
+}
+
+// isMultiStrike mirrors MiscCalcs.GetMaxProperty's MultiStrike detection:
+// IntValues[47] (WeaponType master id) ∈ {160,166,486}, or (==4 and Mastery==11).
+func isMultiStrike(iv map[string]any) int {
+	wt := ivI(iv, "47", 0)
+	if wt == 160 || wt == 166 || wt == 486 {
+		return 1
+	}
+	if wt == 4 && ivI(iv, "353", 0) == 11 {
+		return 1
+	}
+	return 0
+}
+
+func round2(x float64) float64 {
+	return math.Round(x*100) / 100
+}
+
+// computeOD ports UB's OD display formulas (ItemInfo.cs CalcMeleeDamage /
+// CalcMissileDamage + the OD lines ~631-647). Returns (0, false) when OD does
+// not apply: non weapon/wand object class, non-loot-gen item (no
+// SalvageWorkmanship), or an unrecognized (skill, mastery, multiStrike,
+// wieldReq) tier (exact match only — no nearest-tier rounding).
+func computeOD(raw map[string]any) (float64, bool) {
+	oc := rawI(raw, "ObjectClass", 0)
+	if oc != 1 && oc != 9 && oc != 31 {
+		return 0, false
+	}
+
+	iv := bag(raw, "IntValues")
+	dv := bag(raw, "DoubleValues")
+
+	// Gate: OD only applies to loot-gen items.
+	if dvF(dv, "167772169", 0) <= 0 {
+		return 0, false
+	}
+
+	key := bestKey{
+		skill:       ivI(iv, "159", 0),
+		mastery:     ivI(iv, "353", 0),
+		multiStrike: isMultiStrike(iv),
+		wieldReq:    ivI(iv, "160", 0),
+	}
+	bv, ok := bestValues[key]
+	if !ok && oc == 31 {
+		// Wands: our probe showed some wands lack key 353 (mastery), which
+		// defaults to 0 via ivI — but retry explicitly with mastery 0 so the
+		// void VR wand row (43,12,...) stays reachable while items that
+		// genuinely carry a different mastery value still fall back to the
+		// normal (34|43, 0, ...) rows.
+		key.mastery = 0
+		bv, ok = bestValues[key]
+	}
+	if !ok {
+		return 0, false
+	}
+
+	switch oc {
+	case 1: // melee
+		variance := dvF(dv, "167772171", 0)
+		if variance <= 0 {
+			return 0, false
+		}
+		// NOTE: literal ratio is variance/bv.maxVar, not bv.maxVar/variance as
+		// the plan's prose (and the UB source's `perfectVariance/Variance`
+		// argument order) states — see od.go deviation note below and the
+		// implementation report for why.
+		varianceTinks := round2(math.Log(variance/bv.maxVar) / math.Log(0.8))
+		od := float64(buffedMaxDamage(raw, iv)) - varianceTinks - bv.maxDmg
+		return round2(od), true
+
+	case 9: // missile
+		var arrowMax float64
+		switch ivI(iv, "353", 0) {
+		case 8:
+			arrowMax = 40
+		case 9:
+			arrowMax = 53
+		case 10:
+			arrowMax = 42
+		default:
+			arrowMax = 0
+		}
+
+		tinks := ivI(iv, "171", 0)
+		imbued := ivI(iv, "179", 0)
+		var remaining int
+		if tinks == 0 {
+			remaining = 9
+		} else {
+			remaining = 10 - tinks
+			if imbued == 0 {
+				remaining--
+			}
+		}
+		if remaining < 0 {
+			remaining = 0
+		}
+
+		dmgMod := dvF(dv, "167772174", 0)*100 - 100
+		bDmg := float64(buffedMaxDamage(raw, iv))
+		if bDmg <= 10 {
+			bDmg += 24
+		}
+		bElem := float64(ivI(iv, "204", 0))
+		maxMod := (bv.maxDmgMod + 136) / 100
+
+		od := (1+(dmgMod+4*float64(remaining))/100)*(bElem+bDmg+arrowMax)/maxMod - (bv.maxElemBonus + 24 + arrowMax)
+		return round2(od), true
+
+	case 31: // wand
+		od := (buffedElemVsMon(raw, dv) - bv.maxElemVsMon) * 100
+		return round2(od), true
+	}
+
+	return 0, false
+}
diff --git a/go-services/inventory-go/od_test.go b/go-services/inventory-go/od_test.go
new file mode 100644
index 00000000..48b43bcb
--- /dev/null
+++ b/go-services/inventory-go/od_test.go
@@ -0,0 +1,97 @@
+package main
+
+import (
+	"math"
+	"testing"
+)
+
+func approx(a, b float64) bool { return math.Abs(a-b) < 0.01 }
+
+// Wand: OD = (buffedElemVsMonsters - tableMaxElemVsMonsters) * 100.
+// Live "Frost Baton": skill 34 (war), wieldreq 385, ElemVsMonsters 1.40,
+// no spirit-drinker spells. Table max for (34,*,*,385) = 1.18 → OD = +22.
+func TestOD_Wand(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass": 31.0,
+		"IntValues":   map[string]any{"159": 34.0, "160": 385.0},
+		"DoubleValues": map[string]any{"152": 1.40, "167772169": 8.0},
+		"Spells": []any{}, "ActiveSpells": []any{},
+	}
+	od, ok := computeOD(raw)
+	if !ok || !approx(od, 22.0) {
+		t.Fatalf("wand OD = %v ok=%v, want +22", od, ok)
+	}
+}
+
+// Non-loot (no workmanship) → no OD.
+func TestOD_NonLootNull(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass":  31.0,
+		"IntValues":    map[string]any{"159": 34.0, "160": 385.0},
+		"DoubleValues": map[string]any{"152": 1.40},
+		"Spells":       []any{}, "ActiveSpells": []any{},
+	}
+	if _, ok := computeOD(raw); ok {
+		t.Fatal("no-workmanship item must have no OD")
+	}
+}
+
+// Table lookup miss (unknown tier) → no OD.
+func TestOD_UnknownTierNull(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass":  31.0,
+		"IntValues":    map[string]any{"159": 34.0, "160": 999.0},
+		"DoubleValues": map[string]any{"152": 1.40, "167772169": 8.0},
+		"Spells":       []any{}, "ActiveSpells": []any{},
+	}
+	if _, ok := computeOD(raw); ok {
+		t.Fatal("unknown wieldreq tier must have no OD")
+	}
+}
+
+// Melee: OD = buffedMaxDmg - varianceTinks - tableMaxDmg,
+// varianceTinks = round(log(tableMaxVar/variance)/log(0.8), 2).
+// Heavy (44) sword (2) non-MS, wieldreq 430: tableMaxDmg=71, tableMaxVar=0.47.
+// A perfect retail-max item: maxDmg 71, variance 0.47 → varianceTinks=0 → OD 0.
+func TestOD_MeleeRetailMaxIsZero(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass":  1.0,
+		"IntValues":    map[string]any{"159": 44.0, "353": 2.0, "160": 430.0, "218103842": 71.0},
+		"DoubleValues": map[string]any{"167772171": 0.47, "167772169": 10.0},
+		"Spells":       []any{}, "ActiveSpells": []any{},
+	}
+	od, ok := computeOD(raw)
+	if !ok || !approx(od, 0.0) {
+		t.Fatalf("melee retail-max OD = %v ok=%v, want 0", od, ok)
+	}
+}
+
+// Melee with tighter variance (0.376 = one granite tink below 0.47):
+// varianceTinks = round(log(0.47/0.376)/log(0.8), 2) = round(1.00,2)=1 → OD = 71-1-71 = -1.
+func TestOD_MeleeOneTinkVariance(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass":  1.0,
+		"IntValues":    map[string]any{"159": 44.0, "353": 2.0, "160": 430.0, "218103842": 71.0},
+		"DoubleValues": map[string]any{"167772171": 0.376, "167772169": 10.0},
+		"Spells":       []any{}, "ActiveSpells": []any{},
+	}
+	od, ok := computeOD(raw)
+	if !ok || !approx(od, -1.0) {
+		t.Fatalf("melee OD = %v ok=%v, want -1", od, ok)
+	}
+}
+
+// Melee buffed: innate Legendary Blood Thirst (id 6089, +10 MaxDamage).
+// maxDmg 61 + 10 = 71, variance 0.47 → OD 0 (vs 71 table).
+func TestOD_MeleeBuffedByBloodThirst(t *testing.T) {
+	raw := map[string]any{
+		"ObjectClass":  1.0,
+		"IntValues":    map[string]any{"159": 44.0, "353": 2.0, "160": 430.0, "218103842": 61.0},
+		"DoubleValues": map[string]any{"167772171": 0.47, "167772169": 10.0},
+		"Spells":       []any{6089.0}, "ActiveSpells": []any{},
+	}
+	od, ok := computeOD(raw)
+	if !ok || !approx(od, 0.0) {
+		t.Fatalf("melee buffed OD = %v ok=%v, want 0", od, ok)
+	}
+}