BESTFIT Clock Mainspring for SWISS Travel Alarm Clocks No. T390-4

Bestfit System #77 Mainspring for SWISS Travel & Alarm clocks, presumably the TIME side spring, Regular tongue end, No. T390-4, 1960’s or newer, steel. See images for precise mainspring characteristics. I specialize is hard to find watch & clock parts and all parts are unconditionally guaranteed. Images do an adequate job of representing the item