Another enigmatic cartridge is the 10.75x63. COTW sais it was introduced about 1910 and was either a Mauser or a Mannlicher development. It is simply the better-known 10.75x68 with a 5mm shorter neck. DWM case number is 515, while the 10.75x68 is #515A, so it seems to be older than the x68. The only contemporary data I have found is from a ca1930 Burgsmueller, Kreiensen catalog: A 347gr jacketed bullet in front of 58.6gr R5 powder for 2129 fps. This is the same as the so-called "weak" load for the 10.75x68, intended for European use. The "full" load for the 10.75x68 was given as 64.8gr R5, 347gr bullet for 2260 fps. Sometimes the development is ascribed to a lePersonne, London. There is a note in the DWM case book mentioning DWM made 10.75x63 cartridges for lePersonne. LePersonne was an international arms dealer based in London, not quite the type of man who develops new cartridges.
In his standard tome "Das Deutsche Waidwerk", first ed. 1914, F.v.Raesfeld, who was a strong believer in the 9x57 himself, wrote: "The tendency to use smaller and smaller calibres seems to be a thing of the past. It is remarkable, that the Austrians have nearly arrived at the old 11mm calibre again. The Vienna company "Kaletzky's Widow", gunmaker to the court, offers a repeating rifle in 10.75 mm, that is praised as an excellent big game rifle." This meant european big game of the then vast Austro-Hungarian empire, like Hungarian stags and Carpathian bear. Austrians then had little interest in Africa, being without colonies there.
Many years ago a piece of "junk" fell into my hands: A Mauser M1903 Turk action, perhaps "lost in transit" once, lacking bottom metal and most small parts, with a quite unusual 21.5" barrel, full round with an integral full rib and front sight base, proofed in Vienna in 1907. The barrel is inscribed "Joh. Kaletzky' Witwe KuK Österreichischer & König. Serb. Hof-Lieferant in Wien" = Joh.Kaletzky's widow, supplier to the imperial and royal Austrian & the royal Serbian court. A chamber cast revealed it is chambered for the 10.75x63, so this must be the cartridge mentioned by v.Raesfeld and originating with that Vienna company.
In due time I completed the rifle with assorted parts from my "junkbox", to my own then tastes only. I used to shoot some smaller game like roe deer and smaller pigs with it, but now use it mainly for paper punching. My load is a .429" 300gr Sierra, sized-down in a homemade die to .423", in front of 62gr VV N140, for 2200fps.