7-prong Balance Screw Undercutters No. 518 - Watchmakers Tool in box

7 Position Balance Screw Undercutters, No. 518, pre-owend but in virtually new condition and in original box. To use the tool you remove the screw from the balance, put it on the cutter press on the screw and twist it just as if trying to screw it into the cutter, and the graving edges will remove material from underneath the screw. If the screws are gold, which is pretty common,, consider whether you want to keep any of the filings.  Images do a suitable job of representing the item.