Anderson Window Sash Balance

A handy person from 07748 says:
I have an Anderson window where the one sash balance spring is broken on the right side (looking at it from the inside of the home) I wanted to order a replacement one but there is no part number on it. It is stamped Andersen Window and the City and State, but nothing on either side. I have included a picture of both and the window. Not sure if this helps but the Lower window is larger: 35-1/2"W X 39"H with a glass dimension of 32-1/2"W x 36"H (48" diagonally). The upper window is 35-1/2"W x 27"H, the glass is 40" diagonally. Hopefully you can determine which sash balance I need to order, the sash balance itself is 6-1/4"in length. If you need any other info, please let me know.
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Bob from SWISCO responded:

Thanks for posting. I'm afraid that it's impossible to say which Andersen Sash Balance you need without seeing the numbers stamped to the balance box. There ought to be multiple stamps on the balance; we will need a clear picture of each one. Check the face of the box, the tab, and both sides to locate these stamps. If you need help removing and replacing your Andersen Sash Balances, see the video below.

A handy person from 07748 says:
I found these numbers on the sash balances but they were hard to see at first. The Sash balances had two different sets of numbers:

R13/92 P35 7 92
L9/1327 4 6 92

Can that be used to determine which sash balances to use?

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Paul from SWISCO responded:

Good question. Based on your stampings of your Andersen sash balance, our 24-L9-1327 and 24-R13-927 should work in their place. 

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