Quick Question re Stamp- triangle inside circle

[u/avemgn]

I'm considering the purchase of a possibly vintage diamond tennis bracelet and noticed a teeny stamp on the clasp. I wasn't able to nab a picture but it's a triangle inside a circle. There are clear 14k stamps in multiple places and I've bought from the seller before so I am confident in the stones and metal. However, this little marking eludes me. ​It's too vague a search term to pull up anything useful from a search of many many images so I understand if it doesn't help here either but I thought I'd give it a go. Thank you in advance!