Hi Doug,
In my local town there stands a WW1 Mark IV Female tank, it has stood there after being driven to the spot, since 1919. I was asked along with another person, a few years ago, to inspect it with view to doing some conservation work on it. A long story about how the tank is now, but these cracks are common on this early armour. I understood it to be hardened boiler plate and with stress caused by rust building up in joints, etc, these plates have become very brittle, and can literally shatter. Looking at the pics of the Russian ones, I would think they were handled on the frames they stand on, because even with welding them, any stresses on hoisting would create more cracks.
The one I refer to is now an official historic monument and that is how it should be.
regards, Richard