This Stevens manufactured second variation mainspring with the circular radius on the upper forward section is for the Favorite single shot falling block rimfire rifle which not only mounts using the 2nd variation screw and 2nd variation hammer but also has the lever spring mounted on the inside forward belly section of the receiver (the mounting screw tip will be noticeable externally). This mainspring is in very good condition exhibiting a grayish brown patina with light wear. (file photo)

Note: this part is commonly seen on Stevens Favorite single shot rifles with 5th & 6th variation receivers. Additional notes: we have found this in a couple 8th variation receivers.