Here's an A&A Model 453 with a failed toplever spring. I fabricated and fit a new spring, as detailed below.
The failed original part, clearly the failure was the result of the toolmarks left on the surface of the original spring.
A piece of 1095 flat stock was selected then it was heated and forged over onto itself, forming what will become the V form of the spring. It was then machined on both sides leaving enough material to hand file the locating stud.
Once the locating stud was filed, each limb was filed to shape.
The spring was wrapped in stainless wire to hold it while heating for hardening, and quenched in oil.
It was then tempered in a Nitre salt bath for the appropriate time and temperature.
After hardening and tempering, the part is polished (by hand) to deny cracks a starting point and it's ready to reinstall.