Indian Printing Block

After seeing the interesting videos linked by Julio yesterday, I headed down into my storeroom to dig out something that looked familiar ...

I picked up a couple of these blocks some years back, but never got around to exploring what they were, or how they were used. But yesterday's video shows exactly what they are!
Here's a view of the pattern: And a couple of shots of the carving ... They are all slightly warped, so I suppose were discarded at the end of their useful life. They are a very heavy wood, and although it is difficult to tell, I think they are carved on the end grain, as there is a faint concentric ring pattern visible on the back.