Elgin Factory Mainspring for Military Issue 16s Stopwatch / Timer in packaging

Elgin Factory Steel Mainspring for 16s 7j Elgin Timer, Military issue spare part #FO36-7198480, packaged in March 1951, new in sealed packaging. This is if for the Bomber Timer (stop watch) that used a balance similar to a regular pocket watch, NOT for the jitterbug timer which used a little dinky balance. The TM9-1575 Ordinance Maintenance Manual confirms this was made for the Type B movement which was the 7j model, which matches the 1790-16-2 P/N shown on the envelope. I specialize is hard to find watch parts so I usually have whatever you might need, all watch parts are unconditionally guaranteed and reasonable offers are always welcome. Images do a suitable job of representing the item.