Is my Italian ring Sterling Silver or Yellow Gold?

I have a ring that was purchased in Italy a few years ago. It looks to be silver, but the purity marking shows 750 in an oval box. The Marker's Mark shows 85 AR in a square box and ZAD in a square box. Could this be yellow Gold? The outer edge of the band looks to be diamond cut, with a sand paper finish between the two edges. Thank you for your help. Gloria