Topic: Items vs. Foreign Item Codes
In Items and Inventory -> Items there is no place to enter the open stock of the Item and the item_code = stock_id and the hardcoded quantity = 1 whilst is_foreign = 0.
In Items and Inventory -> Foreign Item Codes there is a place to enter stock and the item_code can be blank or be set to the ISBN13 code (or EAN/UPC) whilst the stock_id can be non unique since the primary key is the id field and the is_foreign = 1.
Both these entries get into the same table #_items and are treated individually and both forms have the category field - so the same stock_id can belong to 2 different categories if they come from different forms above.