I don't see a seam on the top rib, so I would guess it is not an
integral demi bloc. But yes, it is a back action.
One thing which is interesting, is that it is helping me date the change over between cm and mm chamber lengths.
This gun is dated 1907, and has cm chamber length ("7").
So I guess the change over to mm was later than that.
This used to be a great gun, but it's well past its prime.
Of course, the seller is out to lunch with the Habsburg provenance.
I bet the LOP is very short too.
Overall, it's at least 3 times the proper pricing and maybe more ("deep pitting in throat").
I think that 98 is the serial number.
Some French companies ( such as Manufrance) reset the SN sequence for each model.
I guess VC did it as well.
Note the (now quite worn out) border in the stock around the sidelock. That's typical for VC..

best regards,
WC-