Weel, hmmm... Good question???
Kind of an oddball for sure..
Its a panzer IV chassis, no question...
And it looks like a Brumbar upper hull...
With a w a A/P firing gun installed instead of the gigantic mortar...
And the gun (pighead) mantlet looks reminiscent of Hetzer, Jagdpanther, or Jagdtiger
My guess??? Is that it is a Brumbar, modified cuz they didn't have much use
for the big pintle mounted mortar late in the war...
RC
Guess I'm wrong, at least I took an honest guess!!!