About this detail of the Tiger
A small proportion of all Tigers were built for use as commander's vehicles. They were fitted with extra internal equipment, including a GG400 generator. The exhaust from this generator was released through a chimney on the hull roof.
The chimney was a very small feature located on the right side of the hull roof, behind the turret centerline.
This is the generator chimney on the Tiger in Kubinka museum. The pipe at the right of the photo (towards the front of the vehicle) is the generator's exhaust outlet. Notice that the end is threaded. Behind it, a welded plate carries a cap attached by a chain. Before submerging the vehicle, the crew would screw this cap onto the end of the exhaust chimney. Presumably the cap had an internal rubber seal. When not in use, the cap was screwed safely onto a threaded stub on its base plate, as you can see here.
This museum Tiger had its Command equipment removed as it was converted to a standard Tiger. From the inside, we can see the bottom end of the generator chimney, now surrounded by the ammunition rack that was not originally installed. The exhaust pipe from the generator would have been sealed to the chimney.(The latest version of this article)