Found this nice Snap-On compression tester -

[goodfellow]

It's hardly ever been used, and I bought it new decades ago, but I just discovered it a few months back when going through some old road boxes. It was nicely preserved. Still very useful and practical if you can get a straight shot at a spark plug hole.

[Snaparxon]

Nice, worth more now in that condition than you paid for it I'm guessing.