Thread: Opinion wanted on these stones

Today I possibly got an amazing gift from my mother.

She is a master book restorer, and one of her friends died a couple of weeks ago and his wife wanted to get rid of all his tools and stuff. So when my mother helped her clear out the garage, the widow asked her 'oh by the way, there are a couple of stones lying in the basement, is there anything you can do with them?'

These stones are very old (at least 30 or 40 years but probably older) and were originally used for lithograph printing. They were sold as rubbish when the lithography business went downhill. They were bought and sold a few times among my mother's colleagues.

Their use of the stones was twofold: to sharpen tools that should be very sharp, and to use them for thinning leather: a very useful property of those stones is that they will not dull a knife when it touches the stone after leaving the leather.

The stones are milky white, but most of the surface is currently covered in sand and grime Only a small strip on the side of stone in the left picture is reasonably clean. when I rub my hands over the white patches, it feels like the belgian coticule, but softer.
The stone in the right picture still has stone lithograph negatives printed on it. These negatives were sanded off for each new printing design.

Perhaps one of the most amazing facts: these stones are 25 cm by 20 cm. one is 8 cm thick, the other 4 cm thick.
My mother thinks that these stones originally came from france and that they were hideously expensive.

I'll try to clean them up sometime this week, though lapping will not be easy. they are almost as big as my sandpaper itself :-)

Pictures are attached. What do you think?