That's a known period pattern, called by some a 'Tank Tread' ring. I believe this pattern of ring had been around since WW1.
This one looks like a well worn, old ring. It should be a two-piece construction, with the skull soldered to the band. It sometimes has a silver content mark of 800 or 835 too. So far so good, but it is also a commonly reproduced ring and there are lots of copies around, so we need better, more detailed photos in order to better assess it for you. If you don't have better photos ask the seller to provide them. If he won't, walk away.
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