14/1 is the gauge number of the actual bore diameter as measured at the proofhouse, using plug gages, 20 cm ahead of the breech end. 14/1 stands for a diameter between 17.80 and 18.03 mm, .700 -.710". As the now CIP minimum bore diameter for a 12 gauge barrel is 18.2 mm, the barrel is undersized by today's standards. As the gun has Damascus barrels, it was certainly proofed for blackpowder only. German proofhouses usually refused to proof damascus barrels for Nitro powders.
The Meffert "Hubertus" safety guns were made to the patent DRP # 7142 of 1879 to the inventor, forester Franz Feist, Sommerschenburg. The cocking mechanism on your gun is apparently made to I.Meffert's own 1879 DRP # 4770. It practically is merely a variation of the Anson & Deeley cocking arrangement. DRGM 32200 of 1894 protected the design of the Omega - shaped, split mainspring.

This is my family heirloom, once bought new by my grandfather's grandfather, so I am the fifth generation to use it. Made and bought in 1893 according to family tradition, evidenced too by the crown/V Vorratszeichen on the action, struck only on completed guns in store in March 1893, ready for sale. The original 16 bore damascus barrels were smashed by a GI in 1945 so the gun is shown with the interchangeable nitroproofed 6.5x52R aka .25-35 Win /16-70 cape gun barrels my grandfather had made by Krausser in Zella-Mehlis in 1940. There are also interchangeable 16-70, nitroproofed shot barrels made at the same time. This gun has the usual Meffert -Hubertus lockwork as shown in post-1900 catalogs, still marked with the "DRP 7142" of the long expired 1879 patent. But it already has that Omega-shaped spring, protected by Meffert in 1894.