Apparently there is even more confusion, even at the Steyr factory: According to the Mannlicher Collectors list linked to by Igorrock above the so-called "Magnum" action in 6.5x68 was introduced in 1958. Mine, clearly a Magnum action with the post-52 side safety and low, straight bolthandle is proof dated 1957, a year before it was introduced according to the list. And, it's receiver ring is clearly marked "Mod.1950"! See this thread:
http://forums.nitroexpress.com/showflat....true#Post160883
I asked the Steyr representatives at the IWA some weeks ago about literature on sporting Mannlicher-Schoenauers and they told me about their own "definite" book on their history. That book set me back Euro 49.- . A big disappointment! Only half a confused page on thes classic rifles. The models 1924, 1925 are not even mentioned . The company, now owned by south-eastern investors, is not interested in their former products, they are only interested in selling their current Steyr rifles that are not related to the classic Mannlicher-Schoenauers any more. At least this information may be of some value: The last true Mannlicher-Schoenauer sporter was shipped in 1973, now 41 years ago, after a total production of "about 73000".