Okay so I've done a bit of side research and here is my hair brained theory. I think this is an indigenous static flamethrower test. (cuprum if you can counter this please do, my google-fu on russian ww1 flamethrowers has been weak so far). I think it has to be a tsarist test of the Tovarnitski trench flamethrower or the General Ershov System. I think the latter is unlikely as from what I've read the General Ershv system had wheels, which the photo seems to indicate this one does not. As far as the Chem suit is concerned it is oddly similar to the first one I posted. At one point you see one of the operators with those odd, lightly colored gloves pulling on some lever. So could this be a Russian Flame-Chemical Training Battalion demonstration of a static flamethrower? I've seen that soldiers of these detachments preferred leather jackets to protect them from the heat of their weapons plus face protection can easily come in the form of a gas mask (hence the Avalov Mask) I'll message my source and see if he has anymore details but what are your thoughts?