Need help identifying channel balance

Hey, Jenny. Your balance looks like your S385-27. You may want our 2610 option, but you should weigh your sash just to be 100% sure.

I'm not sure I understand your question. The 2610 option represents the balance spring's strength calibration; in other words it indicates how much weight your balances can carry. It's not a separate thing that is comparable or different from the S385-27. I recommend the 2610 option based on your old stamp of "261." Your stamp is just an older designation for the more modern 2610 stamp. They just added a 0 to the end, that's all.

If you look on the store page for the S385-27, you can see that the 2610 option indicates that it can carry 5 through 9 pounds. Since you said your sashes are  heavy, then the 2610 option may be too weak. That's why it's important to weigh your sash. You need to remove it from the window and place it on a scale. 

For clarification, the "sash" is the glass panel in your window that you raise and lower to open and close the window. You may think of it as the window itself, but the window is everything: the sash, the frame, the sill, etc. The sash is just the glass panel.

$140 per window to just replace balances is extraordinarily expensive. Are you just replacing the balances? These are less than $10 each and can be replaced very easily. See the video below.

Great, that all sounds good to me. You definitely don't want to order a spring that's stronger than the weight of your sash, though. It won't give you extra support but will instead make your windows harder to close. If they're too strong, then your sash will actually drift open after you close it. I like to think of it like Goldilock's porridge. Not too strong, not too weak; you want it to be just right.

Greetings! Tom had me confirm this--from my calculations, the S385-27 with a spring weight of 2670 would work for your 51" wide sash.

Our pleasure. If you have any other inquiries, do not hesitate to share them with us.