I did look up the dates in the event code for Wallas, but forgot what I found...
I can help out, I saved this nice piece of intel. Belated thanks for digging it out by the way.
Build dates according to LiquidSky's findings (pre 1.05beta):
Russian Mech Corps: September, 1942.
Russian Separate Tank Battalions: October, 1942.
Russian Artillery Divisons: November, 1942.
Luftwaffe Field Divisions: December, 1942.
German Heavy Panzer Battalion: December, 1942.
Assault Gun Regiments (probably Russian) January, 1943.
Tank Corps: January, 1943 (adds an artillery unit to the corp)
The biggest threat for mankind is ignorance.