cougar, not the end of a pendulum, but the end of a plumb line used in carpentry to make something straight up and down or "plumb". That's a "plumb bob".
Oooo, wait, I read the rest of your post (missed it at first, my mistake!) Thought you were mixing the two, sorry.
Interesting idea to think it could be a pendulum weight, but agree with you that it is strange to inscribe/mark both sides as few people look at the pendulum ever.