I recently picked up an "antique" cameo ring (supposedly from victorian era) but the serial makes me suspicious

(Wisconsin)

This "antique" ring has a serial starting P&G 9 375 then 2 symbols (I could be wrong about exactly what it says as it's super tiny and I don't have a magnifying glass) but it looks similar to what I wrote, if not exact. Upon seeing this I am just very skeptical that it is in fact a vintage peice of jewelry. Can anyone tell me more?