I've read where there is a Formula that you can use to determine the mainspring's size. Google should have it, and all you need to do is measure the barrel ( and arbor ? ) and you'll be off to a good start.

To my mind, if you can't order the 'exact' spring, going with the weakest that's the closest makes sense.

Hope you find a good one!

Michael.

 

I've read where there is a Formula that you can use to determine the mainspring's size. Google should have it, and all you need to do is measure the barrel ( and arbor ? ) and you'll be off to a good start.

There is a great video explaining it.

 

This is a Schild ( A.S.) caliber 220 , 18 Ligne ref. 1833.

Watch Mainsprings

Watch Mainsprings

www.vintagewatchstraps.com

Regards enrico

 

This might help (thank you Enrico!)

Hope you can find the right size mainspring.
gatorcpa

 

This might help (thank you Enrico!)

View attachment 19328343

Hope you can find the right size mainspring.
gatorcpa

@gatorcpa, please upgrade your deprecated Ranfft app to The Watchmakers App - as maintainer of both apps I promise - there are no downsides and only gains - it is much faster, takes less space on your phone and has everything your app offers plus much more, and it's being updated regularly with new info.

 

There are more family members to this caliber if that helps finding mainspring:

In tech sheet from 1928 mainspring has part number 70 (all parts just numbered incrementally), but that probably doesn't help anything.

 

for those following I ordered a 220 caliber mainspring and this was the result. So clearly 220 is the wrong caliber as it is incredibly small for the mainspring I pulled out of the watch. I took some good measurements and will hopefully find the correct spring soon