That is a Suntour derailleur adjust key, called a “Sunco key”. You got them with the group set in the 80s. It was used to adjust 5 speed rear derailleur shifting. There were two recessed holes in the main body and this key was used to adjust the cage to cog space. Clockwise took you further from the cog, anti-clockwise took you closer to the cog.

On the other hand I could have just made that up.



Bob - I remember that show