The Soviets used the 76 mm model 1931 and model 1938 mainly for air defense purposes. Model 1931 has been credited as design of G. P. Tagunov, the improved version called model 1938 was created by the Soviet artillery designer M N Loginov. The main difference between the two models was the introduction of a new driving device and some smaller improvements.
During World War 2 both of these guns saw a lot of use with Soviet military.
The Germans also captured these guns in large numbers and armed large number of their anti-aircraft gun units in air-defence of home front with them. German names for these guns were 7.62 cm Flak M 31 (r) and 7.62 cm Flak M 38 (r), after running out of captured ammunition Germans modified the guns to 88-mm calibre. In that new calibre these guns were known as 7.62/8.8 cm Flak M 31 (r) and 7.62/8.8 cm Flak M 31 (r).
In some cases the Russians used them as AT weapons, the gun had a hitting penetration of 78mm at 500 meters and 68 mm at 1000 meters.
The Finish (who captured about forty guns and also bought some more from the Germans) developed an AT round that increased the hitting penetration. Until the introduction of the 7.5 cm Pak 40, in May of 1943, these anti-aircraft guns were the most powerful antitank-weapons in Finnish inventory. (http://www.jaegerplatoon.net/AA_GUNS3.htm)The model below is from pendraken (10mm). It belongs to my soviet army and I used it to participate in the Pendraken Painting Competition 2012.