Your date of 1872 may be a bit early has the firm of Webley and Scott was not formed till later ,their main production were revolvers for the War Department and also rifles.They did make muzzle loading shotguns for export some did have Damascus barrels but most were laminated steel.
In an old American catalogue these guns were advertised as follows
W.&.C. Scott & Sons muzzle loading d/b gun ,fine twist Damascus barrel, patent breech, percussion fence, bar locks, oiled walnut stock,checkered hand, 12 bore 32 and 34inch barrels, weight 7.1/2 to 8.1/2 lbs Price $18 . 66. For a 10 bore weighing 8.1/2 to 9 lbs the price was $20
The load I would recommend for standard 12 bore for game shooting would be 2.3/4 drms of FFFg powder to 1.1/16 oz of No 6 shot
Feltwad