I was looking for a small wrench 3/8" in my small box of those type wrenches and discovered this wrench. I didn't know I had it. I wonder how old it is. My camera is on the fritz, but I found this photo that is just like my wrench.
perhaps a magneto wrench?
I used to have - maybe I still do - a wrench similar to that for CZ/Jawa Czech-made motorcycles, that came with two feeler blades riveted in the middle. One, I believe, was for the plug gap; the other for the point gap. Had it been a four-stroke motor, I'm sure they'd have riveted on a third one, for the valve clearance.