Just visible (and upside down) on Paradox' photo #2 is the stamp, '6.5 M/M', consistent with the 6.5X54 used in the Mannlicher Schoenauer M1900 and M1903 as well as the Y1903 through 1930 'Greek' military MS.

The early MS sporting rifle, carbine, and takedown models corresponded to the MS proprietary cartridges for which they were chambered.

M1903 (also M1900 and 'Greek') - 6.5X54
M1905 - 9X56
M1908 - 8X56
M1910 - 9.5X57 - known to British trade as .375 Nitro Express Rimless