We have a number of broken springs supporting windows that went into the unit around 1980. They are single glazed windows and we do not know the manufacturer. If you can match these spring mechanism from this picture or if you have a better approach let us know. The springs fits into a 3/8" wide channel and we would need 4 at 37 1/2" and 4 at 49 1/2" long measuring from the very top of frame to where it hits the sill.
See attached three pictures showing the top, the bottom, and one of the whole springs with the bottom broken off. The length of the spring is 15" and including the top it is 16 1/2" long. This is the length for the longer of the tracks we sent the measurements for yesterday. The diameter of the balance is 3/8 of an inch.
Andy