Andersen sash balance

A quick learner from New York, New York says:
I have Anderson Windows. The part No. is 11600-17. There is also a number Bl-b 10#31 9 86. Should I be replacing with 24-637 or 24-531?
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Paul from SWISCO responded:

Hello there. With your Andersen sash balance box being marked with "10#33", our 24-1033 will replace it. Take a look and let us know if you have any other questions.

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