I found this small aluminum item in a tool box. It’s 1.5" diameter. The two pieces screw together. I thought it was a little stash container, but the larger piece has a nub inside which would fill the void on the smaller piece when screwed together. Is this some tool? Or maybe a little machinist project.
That’s what they are! I have a box full of leftover parts from years of home repairs, and I frequently store caps of opposite genders screwed together like this.