Need help identifying a tool

Hi all,

One of the members of the local MG club passed away recently, and his friends found several unidentifiable tools in his tool box. He built MGs at the Abbington factory before and after WWII, and also worked on RAF planes in India during WWII. They're not sure if this is something he used to work on MGs or Merlin engines. It looks like it is ~9/16" and ~7/16" and the square end of the tool looks to be ~1/8". The only marking on the tool besides his initials is the number 21. One theory is that it's a tappet tool? Sorry I can't give more details. Someone brought it to lunch yesterday, and I took some quick shots with my phone.

Thanks!

Sparkplug tool?

Slippery wrote: Sparkplug tool?

That's my guess.

yeah to the spark plug tool theory .. looks just like an old version of a spark plug tool that would come with a chain saw

I concur the smaller end is for adjusting the saw chain.

+1 for chain saw spark plug tool. I have one just like that in the garage.

Dang, I was hoping for something more exotic, like a specialized tool for tuning Spitfire Merlins.

Thanks for your help!