Help to ID coil balance

Hello! Your pivot shoe looks like a match for our 15-111, which is designed to be used with the 1/2" thick Series 160 coil spring. As long as your shoe and cover are fine, then you could just replace the Series 160 spring without issue. Look it over and let me know if you had any questions!

Sorry for missing that part of your post. No markings can be an issue. So, in this case, what you'll have to do is get the exact weight of your sash. Any common bathroom scale should do here. Once you get that weight, you then want to divide it by the number of springs you have. Let me know those two numbers and I'll be able to make a recommendation.

Yes, I agree. I don't think you'll miss that half pound of difference. The 4.5 balances should work perfectly fine for you.