Keith: To me, a "bolster" is an engineering term. The British refer to similar features on a gun as "drooping bars", this was mostly in reference to their early backaction ejectors (i.e., 1880s John Blanch and WC Scott guns). Over on the LC Smith webpage they are described as being "convex ribs" (I find that term to be a bit imprecise). They do remind me (as well) of the added metal near to the standing breech on heavy magnums and double rifles, thus my expression for them here. Not sure if there is a proper designation for them. On the few British guns that I've seen and handled that are so-equipped, they are clearly an affectation (still "cool" but purely an aesthetic component IMHO).
![[Linked Image from i.imgur.com]](http://i.imgur.com/ApwQnqQh.jpg)
There actually is a screw in front of that trigger guard (you can't see it in most photography of the Syracuse guns). On Fulton-designed guns it is always well out in front of the guard.
I would assume that an action is filed-up to include them as a means of increasing "rigidity" (these "Syracuse" Smith guns are noticeably more-narrow at their base than the later guns were). Moreover, the trigger groups for these early guns is also set more-forward than on the later guns, giving them a slightly different overall stock-to-action "geometry". Not sure if these "bolsters" are for strength or just for appearances(?) but (much like Keith here) I find them to be rather attractive. The stock heads on these early guns then followed that shape well-back past the front of the trigger-guard(s) which, of course, adds some rigidity there as well.
Sadly, many (if not most) of these "niceties" were dispensed with by the Hunter Brother within a few years of taking-over production. All of the guns became more "square" and broader at the base of their actions, and they were also flattened (no more "bolsters" after 1891, I presume this helped to streamline the manufacturing process?) and then...things really got "streamlined" after the major 1913 "redesign" of all of the models produced in the Fulton plant. Industrial-scale mass-production has its "demands" too, after all.