Thanks for the correction, Andy. The book said "HN Border Infantry (holding forts)".10HN is a Border Battalion not Regiment.certainly not fortress as in 1924 was minor builded the defense line to german state. 10HN Bat.was located in east Slovakia.
Yes, the T block sounds about right for the name (receiver crest) change. We know from photos in this thread that it was after P and before X. ZB clearly had some unused receivers with the old crest which they used to build rifles during the 1935 'emergency' - and those were sold to Spain in 1938. I think that was because they wanted to get rid of all the unused rifles which lacked the lion crest. It may be that the old receivers used to build some of the 1935 rifles had some minor defects which were allowed due to the 'emergency'.Smid wrote that the old name used on Vz23 continued into first 24 contract, i believe the change was done in T range, but could be done some exceptions. Offcoarse the change to limited company was already done in june 1924, anyway new stamps were delivered much later, and since 1925 is used mainly the Československá Znrojovka Brno in 3 rows..