Keywords: Uhrmacherin.jpg Uhrmacherin Public Domain ARC Identifier 518442 Lancaster Pennsylvania - Hamilton Watches Operation - vibrating hair spring - skilled operation - hair spring is placed into a vibrating machine and operator selects the hair spring with an elastcity which would vibrate a balance wheel with period of 18 000 times per hour 1936 - 1937 http //www archives gov/research_room/arc/ PD-USGov original upload log page de wikipedia Uhrmacherin jpg 2004-05-17 15 11 Stefan Kühn 573×399× 53838 bytes <nowiki>Uhrmacherin</nowiki> Watch repairers |