Andersen Double Hung Balance Box E49 9#31 10-86

A home owner from Albany, NY says:
I have to replace several balance boxes in my Andersen double hungs dating from the mid-80s. They are stamped with the following:
E49 9#31 10-86

There is no stamp on the tab end that would suggest a replacement part number.

Thanks for your help.
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Donna from SWISCO responded:
The replacement Andersen box you need is our 24-939.
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