Hi Tom,
Unfortunately as I said above there are no stamps or markings of any kind on any of the parts. What would happen if I just picked something in the middle of the range and it wasn't correct?
It's the balance that is broken. I forgot to say that
You should not pick a random balance. If it is not the proper strength, it will not work.
If there are no stamps or markings anywhere on the spring itself, then we can still calculate what you need. Tell me the weight of the sash and how many springs are used on each side of the window. Thanks!