Is the '3' upside down (inverted) on the MS as well?

A very nice Mannlicher, that (stutzen, I presume?). Made to be used, still in use and useful. If that 'M' visible on your receiver ring is also part of a 'Made in Austria' roll engraving, that dates your MS to a range between 1924-38 (IIRC). Prior MS would not be stamped with country of origin, 1938-45 would be stamped 'Made in Germany'.

I'm fond of the claw mount on my 1922 proofed M1910, as well. Not a 'snapper', mine, it simply lugs at the front (2 slots), drops in at the rear, and has a single push button at the rear mount to release.

Instant 'zero'.

This, from the 1939 Stoeger, appears to be a 'Vienna Snapper'.