Karl Gerät in teensy-tiny scale

Among the stuff I got from the 2015 CWS bring & buy, and the very first piece from that lot to be painted, is this Karl Gerät (lit. "Karl Device") 600mm self-propelled siege mortar in 1:300 scale. It's inscribed beneath with the date 1976, from Ros Miniatures before they combined with Heroics to become Heroics & Ros.

I show it here with a Panzer IV from C-in-C for scale; the tank is 1:285 scale, so there's a bit of a differential, but not too much.

Compared with fancier, more expensive brands like GHQ or C-in-C, the modelling is fairly soft and crude, and certainly showing its age, but it's perfectly acceptable for the wargames table. It could hardly be mistaken for anything else, even with eyes as decrepit as mine. The more recent modelling from H&R is very much better than this old stuff, from what I've seen.

There wasn't a Munitionschlepper in the lot with it, so if I want one I'll either have to buy one or modify a Pz.IV, of which I have a plenitude. I guess it will depend on how enthusiastic I get about it.