TM14 is a wrong pocket TM in Pokémon Gold and Silver.
EffectTM14 will execute code at 03:5ECD in the ROM. This will fall through to code that takes the value of 0xD004 (last loaded Pokémon) and registers it as both seen and owned in the Pokédex.
Hence it is possible to register a Pokémon by simply having it as the last Pokémon viewed in the Pokédex. Another means of registering a Pokémon is to use this glitch item immediately after it is mentioned in the radio channel Oak's PkMn Talk.
If the player immediately uses TM14 after loading the save file, it will result in ????? (0x00) being registered as seen and owned in the Pokédex due to the value of address 0xD004 being 0x00. However its Pokédex entry normally cannot be accessed unless the Pokémon in the Pokédex only consist of glitch Pokémon.
These effects were documented by gifvex.