Diamond Sterling Silver Ring - Hallmark ID (Z or W?)

[dialleup]

Hello! I bought this ring from a vintage shop in New Mexico. The seller claimed it was from the 1960s and that the gems were tested as diamonds. Due to the lack of marks and the location of the purchase, I'm inclined to believe the ring is American.

I'm not sure what the hallmark or that strange dot between the hallmark and the "925" indicate. To me, the hallmark looks like a "Z" or an italic "W" or just two diagonal lines.

Thank you so much in advance!

Overall photo

Hallmark close-up