The Spanish were fond of Rheinmetall!
Not only were lots of 2cm (including Vierling) and 3,7cm as wel as 8,8cm Flak18 and 36 received during WW2, all these guns were licence produced by Spain!
The 2cm and 3,7cm Flak18 as the R-B-Barzan and the 8,8cm L56 FLAK 36 as the FT44 by Trubia...
The smaller cal weapons were mostly Navy.
The so called 15cm Rheinmetall/Trubia L/55 is in fact the 15cm K-18. There were only some 100 (101?) or so produced, so how many and when did they acquire these guns; were they built in Spain under license at Trubia as indicated by the above designation? I saw on the original Spanish site that it was designated as an "M-1953" in Spain.