If there is any lathe where interesting and often complex accessories are needed for its practical use, then those designed for use by watchmakers may well be in the lead. Hence, it was Mr Gustave Scholer who came up with a design to hold a watch "crown" that might today be recognized as a form of collet chuck where a screw-on nose piece secures the part to be held. The advantage of Scholer's design was that it could be fitted to any draw-in collet - and so used on virtually any watch lathe current at the time.
A watch 'crown' (or button) is the often sphere-shaped knob, knurled or grooved to make it easy to grip, that is used to change the time - or some other parameter - on a pocket watch. Its shape made it difficult to hold on older watch lathes, and Scholar's patent successfully addressed this issue. The unit was to be offered as an accessory by several makers of watch lathes, described in books, and marketed in different forms by such companies as Gem and Johnson..