What is the value of a hammerless double barrel shotgun that says Riverside Arms Company Chicopee Falls Mass patented April 20 1915 on the side and is this a Stevens 311?

This is likely a Stevens 315 I also have a hammerless double barrel shotgun but it has J Stevens Arms Company Chicopee Falls Mass patented April 20 1915.The way I was told to tell what model it was,by the length of the upper tang.The model 315 has a 2 5/8" Tang and a model 515 has a Tang of 2 7/8".My gun is the model 315 and from the J Stevens name I have been told that it was made between 1915 and 1936.As far as the value goes I have seen them go for between $250.-$400. I got mine at a garage sale for $100. 5 years ago.