What Mark and Brian said. There are (at least) 3 variants of the Smith barrel loop support. Pre-1913 guns with barrels having a reinforcing wedge probably have replacement barrels or the support was fitted at a later date; possibly after introduction of the Double Barrel Trap Gun in 1920 or the Long Range Wild Fowl in 1924.
The reinforcing wedge is found routinely on guns with beavertail forends, especially the long beavertail schnabel introduced in 1922.
This is the 3rd style solid wedge
Fox wedge for comparison
Crude A.J. Aubrey
Even 'crudier' Crescent
Remington 1894
Threaded Mode