Help with Channel Balance Stamp

A quick learner from Chicago says:
Can you give any guidance as to which product would replace this part? I?ve included a picture of the stamp. Thank-you.
Thumbnail of the uploaded file named 39 DS 41 ? blurry
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Bob from SWISCO responded:

Thanks for posting. This stamp indicates that your balance is a 'dual spring', designed for extra support. I'm pretty confident we can have these made up for you, but they will have to be a special order due to their unique design. I need a little more information to be able to help. First, can you show us a picture of any fitting at the bottom of the balance? Can you show us another picture of how the balance attaches to the window track? Next, can you provide the length of the metal channel, not including any fittings at either end? Finally, can you provide us the exact weight of the window sash? This information will help us get this started for you. Many thanks.

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