To the best of my knowledge, Soma was not a manufacturer, but the brand name of bicycles marketed by Soma Sports Inc. of New York. My first recollections of the brand date to 1978, when they started advertising in Bicycling magazine, using an Eddy Merckx look alike. I still have a couple catalogs from that era. They produced a full line of bicycles including children's, city bikes and lightweight racers. The lightweight lineup included 7 models, with the Sport being 4th from the top, though still an entry level model. Your color looks similar to the catalog sample and if so, the official name is Metallic Dark Silver.

Based on the serial number, the likely manufacturer of your bicycle is Kuwahara. It certainly matches their format. While it is possibly a 1980 model, it was produced relatively late in the year and is more likely a 1981 model.