Those barrels appear to me to be from a Stevens No. 335. The No. 335 was introduced by the J. Stevens Arms & Tool Co. in 1911 --
The No. 335 was wedge-bolted in the rib extension as on these barrels. The No. 355, 365, 375 and 385 were rotary bolted through the rib extension.
The No. 335 survived WW-I and continued to be offered by J. Stevens Arms Co., a wholly owned subsidiary of Savage Arms Corp., through 1931.