Anderson sash balances

A handy person from Pittsford,NY says:
June 13, 2015
The sash cords on two of my Anderson double hung windows have broken.
Assuming there is no way to replace just the cord, I need 4 new balances for two windows.
Are there a left/right pair for each window or can the same part be used for each side?
The left and right have different numbers along one side as shown by the attached photos of the balances in place in the head rail of one window. Each has another number that may be the same but is only legible on one of the balances.
As looking from the inside out:
Left balance P90 R13/927 2-88 & 11600-17
Right balance L9/1327 2-88 & maybe 11600-17

Which number do I use for ordering replacements?

Regards
Doug
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
June 16, 2015
Looks like you have cottage windows where the top sash is shorter than the bottom sash. Therefore you will have a left and right top balance to compensate for that. Based on your stamps, I recommend our 24-L9-1327 (left) and 24-R13-927 (right) for both windows.
A quick learner from Pittsford,NY says:
June 16, 2015
Thanks for your confirmation. You are correct. The top sash is shorter than the bottom. I have ordered two each of the above parts. One of them is on back order.
Regards
Doug
Andersen Sash Balance, L9 1327
Andersen Sash Balance, L9 1327
24-L9-1327
$54.20
Andersen Sash Balance, R13 927
Andersen Sash Balance, R13 927
24-R13-927
$54.20
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