Bob, I agree with you on the cartridge length, according to the drawings it is certain what is written there. In the "New" way, the expression of the designation of the cartridge, i.e. caliber x length and an addition to the border, groove, etc., is a purely foreign designation in the regulations, nor was it used in ordinary military communication in the army at that time.
When I try to approach the development of the marking of weapons / ammunition, at least two marking systems were used simultaneously.
1) Military.
In the translation, the post-war designation of weapons and ammunition was the original designation, including the pattern, and a new addition was written at the end for distinction, i.e. S -Soviet Union, N-Germany, B-Britain, U-USA.
Note the use of millimeters and not centimeters in the notation.
Example:
-37mm PLK vz.39 S
-30mm Kulomet 108 N
-105mm Kanon vz.18 N
-122 mm Houfnice vz.38 S
-20mm OTČSv vz.38 N
etc.
Unlike the German system of trophy weapons and ammunition for 2 SV, the letters are capitalized and not in brackets ..
We are talking about marking according to Czechoslovak military customs.
After the war, until the first half of the 1960s, the marking of ammunition was, let's say, established since the pre-war period. with that excursion about trophy weapons introduced in the Czechoslovakia ... But then came the era of standardization with the Soviet system. And there were changes in the designation of abbreviations, especially artillery ammunition.
Another change in the labeling of the ammunition came about as Bob writes Write the designation of the weapon in the abbreviation after the designation of the cartridge..
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Then we have factory labeling and that was not the same as military labeling. Some factory markings were never used in the military, and the same applies vice versa. Then we have the cover designation of some object that was in the army and in the manufacturing sector.
Akon