Riverside arms was a trade name commonly used by Stevens for their budget-branded or hardware store guns from about 1914 to about 1930. I believe you may have their model 215. The hammerless hammer double was the 315.
as for value, there’s no telling. They weren’t expensive when new, and were rode hard and put up wet. They are not rare and don’t have much value at all today. Nevertheless your photos don’t provide enough detail for a fair evaluation-yours is not in very good condition, from the photos you do provide. Maybe $200 if in working order.