Sash channel Balance

A quick learner from Denver says:
No indentifying marks on the window and nothing but bsi 2640 on the balance. I've tried submitting pictures but the form fails.
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Tom from SWISCO responded:
I'm afraid I cannot identify what you have based on the stamp alone. I recommend that you look at our Channel Balance Home Page and follow the steps in order to find the Series that best matches what you have.
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