Not so unusual at all! The short, telescoping action of the Mauser 66 was invented in 1963 by Walter Gehmann, Karlsruhe, and patented DBPatent # 1205423. At the same time Walter Gehmann held the rights to the vom Hofe trademark and the vom Hofe proprietary cartridges. In fact, the 7x66 vom Hofe Super Express was designed by Gehmann in 1956, based on older prototypes by Wilhem Brenneke. The 7x66 SE v.Hofe was meant as a replacement of the 1931 7x73 vom Hofe SE. The belted case 7x73 needed a long Mauser Magnum action, unavailable in the 1950s. So Gehmann packed the ballistics in a shorter case that would work through a standard length M98 action without opening up. Of course, Gehmann had the rifles for his proprietary cartridges made by Mauser on his own action. BTW, this rifle was proofed HK = 1979.