Riverside single shotgun only marking is 3p?

The Riverside single shotgun marked with "3P" typically indicates the model or grade of the firearm. Riverside Arms Company, known for producing affordable shotguns in the early to mid-20th century, often used such markings. The "3P" may refer to a specific production run or design feature. For exact details about this model, checking with a firearms expert or reference guide may provide more insights.