1. Turn-of-the-century shells were not "low recoil"
Jan. 2 1897
http://www.la84foundation.org/SportsLibrary/SportingLife/1897/VOL_28_NO_15/SL2815017.pdfCharles Grimm defeats Doc Carver in Chicago for the Cast Iron Metal
Grimm used a 12-bore L.C. Smith gun, 7 3/4 pounds,
3 3/4 drams Schultze, 1 1/4 ounce No. 7 shot, in U.M.C. Trap shell.
Carver used a 12-bore Cashmore gun, 8 pounds weight,
4 drams of Carver powder, 1 1/4 No. 7 shot, in U.M.C. Trap shell.
2. For comparison
Pre-1913 Regular frame

Right -1942 12g FW frame Field has thicker vertical head strips; averaging .110 thickness.
Left - 1921 16g FW frame thickness averages .085.
1945 16g FW with more wood

After the sale of Hunter Arms in 1945, Marlin apparently felt the need to address the stock defect by advertising a changes in design for the "L.C. Smith Improved Field Grade" - "L.C. Smith stocks have been re-designed for still greater strength, shaped to hold the frame solidly, with special attention to tight, sure mechanical action. All stocks of selected, seasoned walnut."