Yes, another "panzers only" week here at DAMIJWH!
hmmm... I'm almost beginning to like it...
Panzer: Panzerjäger 38(t) für 7.62 cm PaK 36(r) Marder
Quite a long name for what was basically the fitting of some of the thousands of captured Russian 7.62 mm anti-tank guns in German inventory onto the equally captured (from the Czech) Pzkpfw 38 (t) chassis.
Judging from the dark grey surfaces on the Marders, the photo was taken in spring/summer 1942 when the first Marder III' s reached units on the eastern front. With the Marder series, the German forces finally had a mobile platform capable of stopping the Soviet T-34's facing them in the East, which might account for the happy smile on this private's face.