Lancaster, there may be some optical illusion when looking at collath's photos: You are comparing a matte, rimmed cartridge and a high gloss rimless one. Here are the base dimensions from Dixon's book:
.450 E Express: base 13.9mm = .547",rim 15.65mm = .616"
10.75x68: base 12.55mm = .494", rim 12.55mm = .494"
10.75x52R and 8x50R: base 12.5mm = .492" ,rim 14mm = .551"
The Zultner, Vienna 1929 catalog also lists this cartridge, but calls it "Nr. 593 Mauser, 10.75X52 mit Rand"!
The "11.15mm cartridge loaded with copper-jacket expanding bullets and smokeless powder" in Franz Sodia's 1914 catalog remains a mystery to me too. As he offers it in Mannlicher M95 straight-pull actions it must have the same basic dimensions again like the 8x50R Mannlicher cartridge, as other dimensions would have required a complete redesign of the Mannlicher Magazine and clip. The description with the "copper jacket bullet" IMHO points to some sort of Nitro-for-black load.