It has been about ten years since I have done any serious WWII research outside of work, so if somebody else knows better please chime in. Based on what I can see your notion of it being the 8cm and 10cm mortars is more likely than either representing the Stummelwerfer because the tripod arrangement on the latter is slightly different than what is shown in the set here. The NbW 35 and GrW 34 were also deemed to be virtually identical to each other, which once again reflects this offering.

Given the uniforms on show as well as the fact that the NbW 35 started to be withdrawn from service it looks like the 1941 campaign would be the most likely usage for the larger version of the weapon. That makes elements of the 5th Light and 15th Panzer the most obvious candidates, although the ad hoc Division zb V Afrika and 104th Artillery Command are also plausible. Hope that helps a little.