The No. 520, John M. Browning designed pump gun, was first introduced in the J. Stevens Arms & Tool Co. Catalog No. 52 (Revised Edition) which is circa 1909-10. From the 1912 Shotguns catalogue --
These guns were only offered in 12-gauge. In the 1927 J. Stevens Arms Co. catalog No. 57, they introduce the streamlined No. 620 in 12-gauge and the old No. 520 becomes a Riverside Arms Co. gun, still only in 12-gauge.
In 1928, the 16-gauge is added to the No. 620 offerings. For 1929, the J. Stevens Arms Co. moved the No. 620's safety to a cross-bolt behind the trigger. By June 30, 1930, the 20-gauge version of the No. 620 is ready for delivery.
The No. 520 does not appear in any of the Stevens or Savage/Stevens/Fox catalogues in my collection after its 1927 appearance as a Riverside.
The smooth-top, single hump gun doesw appear in the 1951 Savage/Stevens/Fox parts catalogue as the Model 520A --
We know these guns were made for the government and as "trade brand" guns for Montgomery Ward and others, but they don't appear in any of the Savage Arms Corp. paper I have.
