Stoneware round bed warmer

Hi.

I bought this bed warmer recently in France for 3 euros. I've since managed to find lots of info on the cylindrical stoneware bed warmers but not these round ones.

Mine has no maker's info anywhere, just a mark on the underside which is possibly a French-style number 1. I found a small part of the original cork inside it which had obviously disintegrated with age.

Any info which might help me to find out more about these round bed warmers would be a great help.

Many thanks in advance.

Fair