You can never say with 100% assurance anything about a Mannlicher-Schoenauer as far as calibers or dates or characteristics. The 1950-1950 Improved-1952 and 1956 MC models are all intertwined as Steyr just used up the receiver as they found them. Don't forget that they even had US market and Euro market models. The Magnums were listed in Stoegers from 1959-1968, but as everyone is pointing out, the only real proof is in the proof date on the barrel and receiver. Steyr would make special order guns for anyone with money too, and remember that Stoeger listed the calibers as 6.5mm and 7mm in the catalogue, when the actual availability was 6.5x54mm, 6.5x55mm, 6.5x57mm, 6.5x68mm, 7x57mm, and 7x64mm. Confusing to say the least.