window channel balance
A home owner from SEATTLE, WA says:
March 20, 2016
part is stamped as "20 4 BN CALDWELL"
Tom from SWISCO responded:
March 21, 2016
Thanks for posting. Sounds like you have a 21" block & tackle balance with a stamp option of 2040. I'm afraid that's all I can tell based on your information, though. Now you just need to pick out the top and bottom fittings in order to determine the Series.
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.