Thank you, Maciek. Your second one has rather thrown me. For technical reasons weather charts always have to use a standard time datum, summer and winter; in Germany's case it was DGZ but is now (I believe) CET (GMT+1) - same thing, different name. One of the sets of maps I was using came from the 'Täglicher Wetterbericht' which provided observations and maps for western Europe; this carries the legend 'Alle Zeitangaben in DGZ' and was published by 'des Deutschen Reichswetterdienste'.

The second set was the working charts of the Zentral Wetterdeinst Gruppe (ZWG), and it was this that had the DSZ abbreviation.

Having floundered around after starting the thread I began to wonder if the DSZ was Deutsche Standard Zeit - German Standard Time - basically the same as DGZ, but with the ZWG (Met Office at the Luftwaffe HQ) opting for another variation (just to be different?)

Brian