Welcome to the boards.
You might be right about the Hem Gauge. I did a search & found these but they don't look like yours. The ones on the site have actual "measurements" so your gadget may be used for something else. I have no idea what the other thing is but sure does look old. Does the bottom section have a hinge (or clamp). It looks like it might be a little clamp of some sort & maybe the hole at the top is so you can hang it on the wall. Just guessing here but they look like nice antique pieces.
https://www.google.com/search?q=Anti...yeiLOBAUe6dpM: