Miller, I took a look at my Woodward SXS DR from 1879 (450-400 2 3/8") which is the only Jones I have at this time. The "T" has made a shiny spot on the back of the back bolting slot. That indicates one gun as I described.Perhaps some of the gunmakers will weigh-in on this question.
As far as unloading the hinge pin/trunions goes, the answer is that "draws" are relatively common, but not universal. Vic Venters published an article on "Jointing and the Circle," and included it in his book, "Gun Craft," see page 11. This dealt with the fitting of the front edge of the back lump to the back edge of the "bridge" of the action body so as to "draw" barrels firmly onto face and the hook off the hinge pin. Purdey's (at least for one) currently makes SXS guns with replaceable draws and supplies a series of replacements each larger by a few thou to compensate for wear and restore on-face with a simple drift out drift in part.
The 1909 Boss Over/Under patent calls out an interacting dove tail joint of the action sidewall and barrel breech verticals that are fitted to draw the barrels onto face and unload the studs (trunions).
DDA
