Already in the 1920s/1930s, German manufacturers offered no loaded 14 gauge cartridges any longer, and empty shells only for blackpowder reloaders. England (Eley) may have held out longer.
To research and compare the various old ammunition catalogues from different countries would be interesting, but for that one would best ask in the IAA forum.
Those few empty shells and even fewer loaded cartridges that occasionally show up in eGun, are INVARIABLY more than 100 years old.
Craig's initial question was motivated by a short notice in an older edition of "Cartridges of the World". Now, that one was just one more of many irresponsable lores and pipe-dreams in that encyclopedia. What their slovenly author had in mind, was the French production of 24 gauge cartridges, which still exists on a small, almost artisanal base, besides the Italian (Fiocchi) and the Turkish ones.
