I don't know and I could not care less! The 9.5x57 M-Sch is not even listed in the proof tables available to me. The fired cases show not the slightest signs of high pressure, primers not even flattened. Further, you have to know how the prescribed Maximum pressures were established:
Up to 1939 the gunmaker submitting a gun for proof could specify for which factory load the rifle was to be proofed. F.I. a rifle in 8x60 could be proofed either for the "Normal" loads with a service pressure up to 3100 at, or for the "Magnum" loads, service pressure up to 3500at. See the 1940 RWS and the 1934 DWM handbooks. Only the 1940 proof-law prescribed that each rifle was to be proofed for the highest service pressure load the German ammunition companies offered at that time for a gun so chambered. At the same time the pressure of the highest-intensity German factory load was prescribed as the maximum service load for that cartridge. No ammo factory was allowed to load higher-pressure loads for a given cartridge in the future.
When Steyr introduced the 9.5x57 M-Sch in 1910, the cartridge was undoubtedly loaded to the highest pressure Steyr saw fit for the action. Austro-Hungary at that time had a state powder monopoly, so only one smokeless rifle powder named "Pulver III" was available and consequently used in all Mannlicher and Mannlicher-Schoenauer cartridges. All pre-WW1 rifle powders were fast-burning by today's standards, but the Austrian one was even then infamous for erratic performance. So 270gr at 2100fps was the best the Austrians could achieve with their domestic powder. "In the interest of sighting" the German companies stuck to the same ballistics, but with the better German powders of the interwar years namely 3.25g = 50gr Rottweil R5, achieved these ballistics at only 2700at. The German companies improved the ballistics of some loads of the popular 6.5x54 M-Sch during the 1920s-30s, some loads upped to 3200at, but were not interested doing so with the less popular other M-Sch chamberings. So 2700 at was established as the Max service pressure for the 9.5x57, and 3200at for the 6.5x54 in 1940.
As all Mannlicher-Schoenauer actions, from the M1900 to the last so-called "Magnum" actions, share the same bolt and receiver dimensions, and there is no earthly reason to think that Steyr used different steels for forging the M1924-25 "High Velocity" 8x60, 7x64, 30-06, 9.3x62, 10.75x68 actions and the M1910 actions of the late 1920s, I can not imagine any reason for a difference in rifle strength.