From Bulbapedia, the community-driven Pokémon encyclopedia.
Each item has a number used to identify it in any game. The following list enumerates them according to the way they are stored in any Generation II Game Boy Color game.
Items exclusive to Pokémon Crystal are Teru-samas in Pokémon Gold and Silver.
Index numbers 194 and 195 both contain an item named "TM04". The first index (194) is the real TM04. The second index (195) is a unused and useless item that shares the same name, is stored in the Items pocket of the Bag, and has no USE option. The same applies to index numbers 219 and 220, in which both are "TM28". When held by a Pokémon, the name of both unused TM04 and TM28 is instead displayed as BERRY (Japanese: きのみ Berry). Otherwise, these two "fake" TMs behave like Teru-sama.
Index numbers 250 to 254 have the name of HMs but they are stored in the Items pocket of the Bag and behave like Teru-sama otherwise.
All these items can be sold for 19660.