I won't comment on the circle M, but the "German" markings are definitely fake. The Eagle/N is clearly a poorly done rendition of a German commercial (not military) proof stamp. The stamp itself looks wrong and it seems to have been randomly placed. The other marking, the Eagle/359, is the inspection stamp for Walther. Walther did not make VZ24 receivers, so that inspection is clearly bogus. Plus, the stamp itself just does not look original. Shape and font are all off.
This is clearly a case of someone trying to 'Nazify' just some random non-German Mauser. Very common. Somethings guys just did this cause they had tacky taste and thought it was cool...sometimes they thought it would increase the value.