window sash balance

A quick learner says:
windows were purchased in 1984 Anderson Double Hung
Markings are D31 8#31 3-85
bottom sash glass measures 22x28
I need 2 balance replacements
Window sash balance
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Tom from SWISCO responded:
The stamp 8#31 indicates that you can use the 24-837 as a replacement.
How to replace an Andersen Window Balance
How to replace an Andersen Window Balance
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