I was chasing something else as usual & noticed these pressure values in a "TW" VEB Fahrzeug und Jagdwaffenwerk Ernst Thälmann, Suhl DDR catagloue. So this gives us an idea of what to compare. 3 - 4 pages up from the bottom - gives circa 1975 date.
http://www.germanhuntingguns.com/archives/veb-ernst-thalmann-werke/Kalibre 12 - 850 Bar
Kalibre 16 - 900 Bar
Kalibre 20 - 950 Bar
Any >>bar<< conversion folks that can push that towards PSI??
Also they give that for a few more quid they will attempt to blow it up @ 1200 Bar:
>>Auf Wunsch wird gengen Mehrpreis auch die verstärkte Beschußprüfung mit 1200 bar durchgeführt.<<
Cheers,
Raimey
rse