Italian?

by Cynthia
(Champaign, IL, USA)

I have a gold rope chain that is marked 750 an I know that is European for 18K gold, My question is about the mark that is opposite the 750, it is 151AR. I have spent 2 hours looking on the internet without success. I even called a local jeweler. Is this a country code or a manufacturer or designer? I would love to know.

My father traveled to Italy and Arabia at that time (1960-1980) but it could be local too. Thanks