Raumpanzer Tiger (P) "Rammtiger" (lower left-hand corner) was actually built, as the name implies, on the Porsche Tiger hull, of which about 100 were made before the contract for the Tiger tank was definitely given to Henschel & Sohn. Most of these hulls were converted to Ferdinand/Elefant heavy tank destroyers, 1 or 2 kept as original and 1 or 2 converted to this rubble clearing tank. A modified hull was used to build a prototype self-propelled gun, known as the Grille 17, with a 17cm howitzer. There were plans for a 21cm, 30.5cm and 42cm variant, the latter two being siege howitzers. To my knowledge these were never built.

The large hole in the front of the vehicle, where you would expect the most armor to be, is so the crew can actually see in front of them. I believe the machinegun was still present in the ball-mount on the front of the hull as well, so this too could be fired through the gap. Since taking fire was not expected to be as common in its intended role, this hole was not a big deal, and I believe it lacked the bolt-on 100mm armor plate as well, leaving it with "only" 100mm of integral armor. The rubble clearing purpose of the vehicle made roof-armor more important than frontal armor, hence the fully enclosed design of the vehicle, and the hole in front.

Aha, I haven't seen Kilroy in a while.

Added to "Translation Difficulty" pool due to the absurdly small text in multiple areas.