I was just looking at the 1953 Winchester Model 21 booklet and noticed there were no roll-stamped markings on the left side of the left barrel of any of the guns showing the 21-1 through 21-6 engraving patterns. Other places in the booklet where the left side of plain guns are pictured the roll-stamping is visible.

As to the forearms, a friend of mine has a fully optioned up Parker Bros. BHE-Grade pigeon/trap gun that has two complete forearms, one slim and one beavertail.