(hex:9F) is a glitch item in Pokémon Yellow. It is an unterminated name glitch item.When a 0x50 sub-tile is early in the saved screen data, it will give Professor Oak's unusable message; seemingly with the same 'use' effect as an Old Amber. However, the scientist in Cinnabar's laboratory will not accept it.
When the 0x50 sub-tile is not present in the data, this glitch item may freeze the game.