I have a relatively new mainspring for sale, from my Model 54.
This is a stock, factory spring, not an aftermarket part.
The spring is in good condition, I have only about 500 shots on it. It is not broken, and should serve you well if you desire an exact replacement for your stock, factory spring. Includes the guide and washer.
Cost is $15 for everything.
Shipping will be an additional $5.00 to anywhere in the continental U.S., possibly more for overseas/foreign addresses.
If you have a broken mainspring, or maybe you want a backup, this is your chance to get it without spending a bundle of money.
I prefer PayPal, but will be glad to accept a money order. Shoot me an email if you're interested, and I'll post on the forum when it's been sold.