This is not the same as the 9.5x51R MB (MB105) which has a 3-4mm longer neck. It does match the 52mm case profile and is believed to be equivalent to the 9.5x52R. Several of these 52mm MB ‘Einheitshülse’ case types appear to have a case length closer to 51mm than 52mm (especially Austrian production) so this would not be unusual. – WB DIXON