This Stevens manufactured first variation mainspring screw is for the earliest of Favorite single shot falling block rimfire rifles which use the 1st variation (bow style) mainspring and do not have the fixed integral lug on the lower tang. This mainspring screw is in very good condition exhibiting a grayish brown patina with slot wear. (file photo)

Note: this part is commonly found on Stevens Favorite single shot rimfire rifles with 1st & 2nd variation receivers.