This rifle was proofed in 1957, so it is an early Magnum action, but with all post-1952 details, except the stock. The stock has the slimmer butt and foreend of the 1950 model, not the later, fuller foreend of the "models" MC, MCA, and GK. These model designations did not refer to different actions, but only to different stock shapes! The sometimes seen Modell NO seems to be for special order rifles that did not fit into the standart catalog patterns, such as a full-stocked 9.3x62, 24"barrel I know. So I think: As my rifle had a 1950-style stock, someone at the factory stamped on Modell 1950.
BTW, as both the M.C.A. and the GGCA usually ask me about such niceties, there is little use asking them. But the MCA knows about this rifle anyhow.