I gave several hints in a couple of my replies today. Kinda makes a persons mind go round and round just thinkin bout it don't it? Just don't let the wheels of yer mind go faster than whats really turning them.
thing that measures circumference of banister rods, glass guage is bubble level? Scores wood on a spinner with nail end with level on other side to keep route level.
From your clues I'm going to guess some type of RPM gauge but I'll be dammed if I know how to use it or on what.
Compass. The type to draw circles. Sorry, too young for beetles references to help me. I'm glad Kanye West introduced us to Paul McCartney.
XXL was closest I guess. I no longer have the box but did find some pics of an original box on the net. The pin spins a little indicator out in the small tub and gives an RPM reading on a scale printed on the tube. Not super accurate but gets things pretty close.