In 1945 Germany had a clear lead in large calibre aircraft guns with 3 different guns in service, the Mk 101, Mk 103 and Mk 108. The allies did not have any such guns.
Germany was also developing the MK 213/30 (30mm cannon) which was a revolver cannon developed by Mauser at Obendorf. The 213/20 (20mm cannon) was also being developed as a possible high velocity gun.
British teams visited Obendorf in the summer of 1945 and sent back to Britain material and drawings relating to the MK 213/30 and MK 213/20.
By September 1945 a programme or work had started with pressure barrels being ordered for the German MK 213/30 cartridge. A quantity of proof projectiles and brass cartridge cases similar to the steel cased German MK 213/30 cases were also ordered.
By October 1945 it was decided that the particular German MK 213/30 gun to be used as the basis for the Aden gun would be the V.6 type (Prior to the V.6 type of which Mauser had made 10 before the end of the war there were 5 earlier prototypes).
The photographs show a war time dated Mauser 213 (30x85) next to a post war experimental Aden LV round (30x86). Its clear who copied who!!
Both INERT and legal to own.
Dave.