From page 323 of Mauser Military Rifles of the World, 5th Ed., "Just before start of WW II, the Yugoslav Government decided to convert its stock of former WW I era Imperial German Gewehr 98 service rifles to its M1924 Short Rifle configuration. Receivers on those rifles were marked "Model 1924 b" as shown above". The picture shown is pretty much exactly identical to OP's picture of his receiver crest (except for OP's drilled and tapped holes, of course). No pictures in MMROTW showing the rear bridge, but I suspect it should have a charger lip on that bridge - all the other Serbian / Yugo rifles do, the Gewehr 98 did, and pictures of Yugo soldiers show them wearing bandoliers with cartridges in the chargers (stripper clips).
Also, I think the OP's receiver is missing the bolt stop on the left side - not real sure what that is about - I expected to see the "ears" sticking out for attaching that bolt stop box and screw... Also, OP's pictures showing filing or grinding done behind right side of rear receiver bridge - as if receiver done to accommodate a "scope friendly" bolt handle, that the particular stock is not ready for. Pretty certain the Gewehr 98 had straight bolt handles.