Thanks to Alfons Bytatuas for letting us know that the were a few small stones up for grabs in a local antique shop. All of them had engraved images of locks. Most likely these are French and were made in the middle of the nineteenth century.
It seemed a shame to grain the images of without trying to revive the images and pull a few impressions. We were able to do this and have them available if anybody is interested
The stones have now been levelled and resurfaced ready for new images.