Need to identify Andersen sash balance

A handy person from Fairfax, VA says:
I have Andersen windows in my house. They are in great condition, except for strings. Looking at the sash balance I see the following numbers stamped:
"5", followed (after some space) by "27" and in the corner "-1168" in smaller numbers.

It's difficult to see them on the picture, but with this description, you should be able to see it.

What replacement part should I use?

These windows were installed before I bought the house (2004), but I have no idea when. The house was built in 1972. May be they are original?

Thank you!
User submitted a photo of a window balance.
A handy person from Fairfax, VA says:
Visible glass width: 31 7/16
Visible glass height: 21 15/16
Profile picture of Donna
Donna from SWISCO responded:
Based on your stamp of 5 27, I recommend our 24-531 Andersen Sash Balance.
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