How do I identify what Andersen balances I need?

A home owner from Maryland says:
I have a few different size Andersen windows that require balance replacements. What's the easiest way to find out which balance I need for each window.
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Tom from SWISCO responded:
Thank you for contacting us. There really is not fool-proof way to identify your Andersen sash balance . We think that the best method is to remove the balances from your window and let us know what each stamp printed on the box reads. There is usually a very specific stamp that lets us know which balance acts as the appropriate replacement, but it's often tricky to find. You might find it easier to send us pictures of the stamps.

Please make sure to also see our tutorial video on how to replace your Andersen sash balance.
A home owner from MARYLAND says:
I've just removed an old balance from Andersen Window. The numbers stamped on the old part are U277P27875. Overall size of window is 46" x 32". Which replacement balances will I need to order? Thanks.
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Paul from SWISCO responded:
Thank you for getting back to us. Unfortunately, I'm having a bit of trouble identifying what balance may match that stamp. Could we perhaps see a picture of that stamp? Seeing how it's printed may shed some insight on the matter.
A quick learner from Maryland says:
I don't believe the numbers will show in a photo. We had to use a magnifying glass to read these.
The letters and numbers are different sizes.
a large U, small 27, large 7P27, small 8, large 7, small 5.
The glass measures 28 1/2" height, 20" wide.

Years ago I had some work done to the windows and a new balance was left with me. It's number is
BK8 837 1196. Do you think this might be the right size for this window?
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Paul from SWISCO responded:
Aha! I see. That clears things up considerably. With the stamp 7P27, I think you should look at our 24-737 Andersen sash balance, which can be used to replace balance boxes with the stamp 727.

As for the other balance, that seems like it would be our 24-837 , which can replace balances with 837 printed on the box.
How to replace an Andersen Window Balance
How to replace an Andersen Window Balance
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