It's a Springfield - Stevens Riverside Model 520 if it's the concave/squared off receiver back, 620 Stevens if its the streamlined convex receiver back. The Riverside guns were the cheaper line, later replaced by the Springfield name around 1930.
It is a C&R, no question.
The company name was the J. Stevens Arms & Tool Co. up until WW-I. At that time their factories were taken over by New England Westinghouse for war production. After the Great War, Savage acquired the factories in Chicopee Fall, Mass., and set up the J. Stevens Arms Co. a wholy owned subsidiary of Savage Arms Corp. In addition to Stevens firearms these factories turned out a lower priced line of guns under the Riverside Arms Co. name up to about 1930 and the Springfield Arms Co. from 1930 to WW-II.
The J. Stevens Arms & Tool Co. introduced a 12-gauge John M. Browning designed pump gun around 1911 or 12. The basic gun was called the No. 520 and listed at $25. The No. 522 was called the "Trap Shooter" Grade and featured a solid rib barrel, and a checkered straight grip stock and checkered forearm, for $40. Higher grades were the No. 525 for $50, No. 530 for $75 and No. 535 for $100.
By the 1914 Catalogue No. 54 they had introduced a 20-gauge version called the No. 200, chambered for 3-inch shells.
After the Great War, the J. Stevens Arms Co. only kept the No. 520 and 522 in the line. By 1927, catalogue No. 57, the J. Stevens Arms Co. introduced a streamlined version the No. 620 and the old No. 520 became a Riverside.