Which spring should I order

I'm afraid that this data isn't enough for me to determine a match. As we are a photo identification service, photos are necessary for us to find you the hardware you need. 

Please make sure to remove the hardware in question from the window ahead of time to ensure that all components are clearly shown without obstruction. Seeing all related components (spring cover, whatever shoe the spring is attached to, etc.) will also be necessary.

That's a huge help, thanks! You have an old, discontinued assembly, but the good news is that we sell modern components that will work just as well. See our 15-177 pivot shoe, as well as our Series 152 coil spring. These should replace your original assembly without issue and with no need for alterations. You can reuse your old cover since it appears to be in good condition.

As for what Series 152 weight rating to use, "H" suggests that it might be an 8 pound spring. However you should weigh your sash to confirm. You can divide that weight between how many springs support it to verify precisely how much weight each spring has to carry.

For example, if you only use 1 spring per side and the sash weighs 16 pounds, then an 8 pound spring would be perfect.