This is a page holder or book clamp, it keeps the book open at the page you want, and it has been a life/time saver during my 20 years + as a book translator. It has kept open more than 100 books for me. It hangs on the wall in my study when I am not working. It's made of brass or similar alloy and it's incredibly ornate, so I drew it with gold and bronze pencils. I don't remember where I bought it, but it has been a most faithful companion, so it must be my favourite tool.