Possibly misunderstood units: ata/atm/technical atmosphere/standard atmosphere

[DTsang]

It seems that a widely spread understanding of German wwii manifold pressure unit "ata" might be wrong.

various sources, including this one:
http://forum.1cpublishing.eu/showthread.php?t=22308

show the following conversion:
1 Ata = 29.92 inches Hg = 760mm Hg

But a few sources suggests that "ata" or "at" refers to "technical atmosphere", while "atm" refers to standard atmosphere.
1 ata=1 kg/cm²=0.96784 atm=735.559mm Hg

http://www.sensorsone.co.uk/pressure...sure-unit.html

http://books.google.com.hk/books?id=...%20ata&f=false

these 2 sources are good, but seems not conclusive.

more about these 2 units in wikipedia:
http://en.wikipedia.org/wiki/Technical_atmosphere
http://en.wikipedia.org/wiki/Atmosphere_%28unit%29

Read between the lines there is another argument: standard atmosphere as a unit is adapted in 1954, after wwii, so the wwii unit "ata" is much less likely to be standard atmosphere.

I think more direct and conclusive evidence, say a unit conversion equation in a wwii German aircraft engine manual, is needed to confirm this, but I could not find it.

Any comments everybody? Anybody familiar with German wwii aircraft engines?