tuning fork

Hamilton-Ricoh Electric ― Citizen X8 / Cosmotron / IC-12 ― Seiko EL-310, EL-320, EL-330, EL-370, Elnix ― Citizen Hisonic, GX Cosmotron ― this is the thread for those watches which are powered by electricity, but which use a mechanical timebase (balance-wheel or tuning-fork) which communicates...