Window has these letters NWDA
Rail size metal to metal: 21 inch
Size with plastic supports 22"
Rail size wide 1/2 inch X 5/8 inch deep
Thanks,
Iggy
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Casey from SWISCO responded:
April 3, 2023
Hello, It looks like you have either our S351-21, with a 15-002 bottom attachment, or S390-21, with a 15-001 bottom attachment. Take a look at the image below to determine which balance you'll need. You'll also need to locate the strength code on your mental channel to choose the corresponding strength option. There is a chart on the product page that explains how to choose your option based on the sash weight. Thank you! 
Comparison of the S351 and S390 balance shoes.
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Casey from SWISCO responded:
April 4, 2023
Unfortunately, your 2090 stamp is from an outdated weigh system that is no longer used. With that being said, you can follow the chart under the S351-21 product description that shows the strength option needed based on the weight of your window sash. For example, the 2060 option that you mentioned would support a window sash between 27-30 lbs. |
