db/item_trade.txt or in rAthena... db/re/item_trade.txt or db/pre-re/item_trade.txt
//Item Trading Restrictions File
//Specify here special rules for item trading.
//Item ID, TradeMask, GM-Level Override
//Trading mask values:
//1:Item can't be droped
//2:Item can't be traded (nor vended)
//4:Wedded partner can override restriction 2.
//8:Item can't be sold to npcs
//16:Item can't be placed in the cart
//32:Item can't be placed in the storage
//64:Item can't be placed in the guild storage
//128:Item can't be attached to mail
//256:Item can't be auctioned
//Example:
//1161,67,50 //Balmung: No drop, No trade, No Guild Store (1+2+64 =67),
//only GMs of GM-level 50 and up can override the setting.
2629,3,99 [Megingjard Item ID#, Trade Mask (Item can't be dropped nor vended), Only GMs level 99 or higher can drop this item]