Trephine
The person who posted this image didn’t actually have possession of the object. Their friend shared it with them, asking the OP whether they knew what it was. Instead of simply replying no, they asked the internet, and they got their answer in literally minutes after posting.
This, folks, is called a trephine. It’s a surgical tool that’s used to drill holes into a patient’s skull to relieve pressure. What sort of pressure, you ask? We don’t know, we’re not surgeons, but it’s pretty safe to say that this lobotomizing instrument belongs nowhere in the hands of the public.