It's a bit large for a finger ring, but it might be a scarf or kerchief ring where the soldered-in ring part came loose. I believe one can still see the remaining grey solder. An email to your town public works office's "Sidewalks Division" asking when that stretch was last paved might go some way towards dating it. Find any dated coins nearby? I get a '30s or '40s Woolworths 5&10 or perhaps later '50s Avon vibe from the pebbled casting and mixed Greco-Roman/American-coin-with-stars motif.