Again, from 1939 Stoeger:

Note caption: (Mannlicher-Schoenauer 6.5X53 and 6.7X53 are one and the same cartridge.)

The same is also true of 6.5X54 and 6.5X53 as some references of the time measured length to bootom of case head, others from recess above. Some listed width by land, others by groove; some 'rounded up', some 'rounded down'.

Brits liked to call it .256 in their listings, just as 9.5X57 was '.375 Nitro Express Rimless'.