The only marking is 1620 on my window channel balance

A quick learner from COLORADO says:
My channel balance length is 17" long, and 1/2 inch wide. I need to purchase two of these. Thanks for helping.
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Emily from SWISCO responded:

Hello!

It looks like you have our S370-17 channel balance with a spring strength option of 1620.

If you have any further questions just let us know! 

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