Once upon a time there was a Riverside Arms Co. But going by Memory ( sometimes a bad thing ) they folded around the turn of the last century. Stevens then used Riverside as a trade name for their less expensive shotguns prior to WW2. 3 inch shells? I don't think so. It was manufactured prior to their being such an animal. I don't think I would have it opened up to 3 inch shells because of the age and also because it was never made for that type of pounding. They may not feed properly with out work, but that I don't know for a fact. JMHO 2 3/4 will do everything a 3 inch will do for most uses, I wouldn't even worry about using 3 inch. Could be wrong, been wrong before
