Post: #2

From what i know there are no classes and/or inheritance, each ITEMDEF block just refers to one of the item entry in the Art and Tiledata files, from the first it takes the appearance of the item while from the latter it takes the basic properties (name, weight, etc) and behaviour.

All of this depends from the ID value of the item, you got a gold coin because "i_base_container_respawning_loot" it's not a valid art/tiledata entry, so you must assign to your custom items a valid ID.