Ron - here’s some vom Hofe history from my database which should answer your questions:
Re date codes:
M M = 1934 (I would like to see an image of that headstamp please)
K T = 1971
******************Vom Hofe History
Ernst August vom Hofe was a Rifle and munition designer who was best known in the 1930’s. He had been an assistant of Herman Gerlich in Danzig in the 1920s and had also worked with Wilhelm Brenneke in Leipzig.
Inspired by the HALGER high velocity calibres, Vom Hofe together with Richard Schienmann formed the firm HOFMANN WAFFEN und MUNITION in Berlin c1930 (ie HOFe-SchienMANN). They entered the weapons market in 1931 with the “HOFMANN” rifle chambered for their own cartridge, the 7x73 Super Express (W30). This had a belted case and was produced by DWM.
Around 1933 they began experimenting with smaller calibres. Firstly with 6.2mm diameter bullet versions of the 6.5x61 and 6.6x61R DWM cases (#431L & #431M : W45 & W46) - which in turn were based on the 6.5x55 Scandinavian case. Neither the 6x61 (W71) or 6x61R (W72) were considered suitable and were not commercially introduced. Attention was then focused on 5.6mm equivalents. The 5.6x61 and 5.6x61R vom Hofe cartridges were developed c1934 (some say 1937 but “M M” hs are reported to exist - this is a point of debate).
By 1935 the partnership with Schienmann finished and Vom Hofe formed the VOM HOFE WAFFEN und MUNITION. He then produced his own rifles for use with his own custom designed ammunition (produced by DWM) and the 5.6x61 and its rimmed counterpart were commercially introduced.
In the c1939-1941 period due to the lack of success with the long case belted 7x73, vom Hofe worked on a shorter rimless 7x67 Vom Hofe Super Express (see W85) and also evidently a 7x75R (see W97). However WW2 intervened and such sporting cartridge development was suspended by DWM in 1942.
All Vom Hofe calibres were unique case types being based on modifying already existing case types. Vom Hofe did continue to collaborate with Brenneke during the 30s and correspondence between the two exists up to 1942 but by then their relationship was strained.
Vom Hofe died in 1945 and in 1955 Walter Gehmann of Karlsruhe took over the Vom Hofe tradename. Gehmann reintroduced the Vom Hofe rifles and 5.6mm Vom Hofe calibres but didn