The T-34 and KV-1 may have been a surprise for the Germans at the start of Operation Barbarossa, but fairly good information was obtained very quickly. As early as June 23rd, 1941, the Germans inspected knocked out tanks and came up with information that may not have been extremely accurate, but was close enough for preliminary work.
"A tank from a swamp near Hanunin. Width: 3.4 meters, length: 6.5 meters, width of track: 70 cm. Mass is about 40-45 tons. Armour: 60 mm front, side, and turret. Armament: 7.62 cm L/26 gun, gun is numbered 69/41. 3 machineguns: one coaxial, one near the driver, one in the back of the turret. Optics: sight and two turret periscopes.
A tank on the south-western outskirts of Razdekhov. Width: 3.05 m, length: 5.85 m, width of track: 55 cm. Mass about 35-40 tons. Armour: side 50 mm, front 50 mm, turret 40 mm, with electric traverse, welded. Armament: 76.2 mm gun with markings 1941-ВЕОСГОЛБ-БЕЗЗАТВОР, 2 machineguns, one coaxial and one next to the driver. Optics: gun sight and periscope. Engine: V-12. Track links are flat with the ability to install grousers. 5 road wheels with rubber rims. The tank could be put into motion."