American PW Elgin, 12s, Grade 345, Mainspring

[horologintex]

Hi Folks!

Need some help on the correct mainspring size for an Elgin Pocket Watch. The serial number is 26313570, and from www.elginwatches.org I have determined that it is a 12s, 17j, grade 345. But I cannot find what size mainspring I need for replacement. Also, I have heard that the manufacturer(s) of replacement PW mainsprings have stopped production because it was no longer profitable. Is this true? And what remaining sources are there for replacement mainsprings?

Thanks (mainly a clock guy, but have taken the FSW Pocket watch class several times...)

 

[Dave Coatsworth]

This is one of those grades that changed midstream. Early models used the #1720 and later models used the #2339. My guess is that your SN is late enough that your watch would need the #2339, although this is not clear in the Elgin material book. If you have your old mainspring out, you can measure it to get a definite answer. The #1720 is 2.23mm wide whereas the #2339 is 2.05mm.