Hi Joseph,i am not a "specialist" in A.A.Russian guns,but "yes" it´s the 76mm field gun.
The first model from this Russian 76mm gun was this one:
The original Russian 3-inch gun model 1902
To the "Russo-Balt truck",they adapted the same A.A.gun,but allready modified and modernized. The maximum range of this gun reached 14,000 metres.
The 76mm A.A.gun incorporated into the Russo-Balt T is this one above:
The modernised 76 mm gun model 1902/30.
The 76.2 mm Gun Model 1902 was the most famous and one of the best Russian three-inch field guns.After this first model,the red Army made several models based on it.