The salt and pepper has been cleaned from these mills. 

The salt can be accessed by removing the lid. Beware, it squeaks like a loud mouse. Pets will come to investigate.

The pepper grind is adjusted by moving the handle once the salt lid is removed. The rod is fairly tight.

Pepper can be added by loosening the grind enough and unscrewing the guard for the grinder. It's a tad tight to adjust. Currently set at a medium grind.

I'm not sure who makes this or if it was a hobbyist piece.