Sash balancers - 531 or 737?

A quick learner from Ohio says:
May 7, 2018
I have the sash balancers removed from my Andersen windows. The number stamped on it is BJ 95#27 2 87.

From my research this 5#27 appears to be matched with the 531 part.

However when I measure the lower sash (visible glass) it is 21 15/16" high x 20 7/16" wide, which leads me to a 2042 size window which calls for the 737 part.

Please advise which part I need! Thank you.
Thumbnail of the uploaded file named IMG_1450.JPG
Profile picture of Paul
Paul from SWISCO responded:
May 10, 2018

Since your window was made in 1987, we advise going with our 24-531 Andersen Sash balance. The newer models have used heavier glass. 
Andersen Sash Balance, 519, 523, 525, 527, 531
Andersen Sash Balance, 519, 523, 525, 527, 531
24-531
$54.20
How to replace an Andersen Window Balance
How to replace an Andersen Window Balance
VIDEO
WATCH >
Andersen's Narroline Sash Balances
Andersen's Narroline Sash Balances
GUIDE
READ >
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)
Current wait time is 3-4 business days
We promise that one of our experts will personally get back to you as soon as they are able. Thank you very much for your patience and understanding. If your inquiry is time-sensitive, please feel free to reach us at (888) 991-1929 or at help@swisco.com.