I recently bought a Spong coffee grinder from Ebay. They follow a design from the 1840s and changed little over the years. I believe they were last manufactured in the 1970s.
The grinder is of the burr type- this is the best to ensure consistent coffee.Some grinders come without the adjustment screw on the back. This presses against a flexible metal flap which adjusts the grind size. While I have not yet found what thread size is used (it could be Whitworth, BSF or many others!), the other bolts on the grinder are all the same size and can be used in its stead.