Good morning, Olgrouser.
If you're the gent from whom I bought that Tobin No.19,4XX, then YES, it has been a while. Fondly remember that trip, introduction, visit, and education.
Most Tobin shotguns will exhibit the female forearm. Post Tobin factory closure when Crandall was later assembling "Tobin" shotguns in his OWN Woodstock shop, I think Crandall used up/ran out of an intricate milled steel component part. That part would have been very difficult to make in a one-man band gunshop, so Crandall had to shift gears with a slightly modified cocking system. Hence, the male forearm.
There will be NO doubt whatsoever whether the Tobin forearm is male or female. The Crandall assembled Tobin gun "male forearm" will have two very short round metal rods, maybe 0.25" or slightly smaller diameter and extension, projecting rearwards from the back of the forearm. The back end of the female forearm will NOT have this "male" feature....but will show two rectangular "holes" of short depth.
I suspect Crandall did a LOT of Tobin gun repairs on guns that had seen a lot, and even moderate amounts of use during his mid 1920s to late 1940s Woodstock gunshop ownership. It's also entirely possible that his revision/modification of the original mainspring cocking system was applied during repair to earlier Tobin guns when he ran out of original Tobin manufactured parts.
Hope this helps.
