Everything looks good from here - I enlarged the pics & nothing stands out except the clasp, as you mentioned - probably had a sport ring clasp originally; maybe a hook. Chain looks right. That center metal piece with the Czech stamp is a bit odd with the other 'lacy' metal bits, but appears to be the same metal under magnification - I do notice the jump ring on the right side of the center piece (in rear view) is slightly bent open, but that's nit picking - especially since I see at least one more with the same issue, and they appear to be same metal, size, etc...So I think it's gorgeous and original. I have had many of these with the same Czech mark. Good luck 🙂
