Replacement channel balance, 2740

A quick learner from pittsbug, CA says:
I need to replacement my channel balance and order take out clips. My channel balance is 28 inches and the stamp reads 2740 B.S.I. and a upside down R
A customer submitted photo of channel balance attachments.
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Paul from SWISCO responded:
Thanks for posting! Please take a look at S390-28 channel balance with a 2740 stamp option. Do you think this would work for you?
A quick learner from Oxnard, CA says:
I have the same 2740 balance as the previous poster. However, I have an upside down Y after the number 2740. Does it mean anything important? Would you suggest the S390-28 also?

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Tom from SWISCO responded:
Thanks for posting! Actually, you may not have the Series 390. While your stamp is the same as his, you may have completely different nylon attachments. You should look at the top and bottom attachments for the Series 390, the 19-002 and 15-001, and note their dimensions. Then, compare them to yours. Do they match up? Do yours have wings, or no wings? An important dimensions is the depth of the bottom shoe; in this instance, the depth of the 15-001 is 1-1/8". What is yours?

As for the upside-down Y after your stamp, I'm not really sure what that could mean. It's possible that it's just a manufacturing indicator, but I could be wrong. The best way to determine if the 2740 is the right stamp for you is to compare its strength to your sash weight.

The 2740 can carry a window sash weight range of 19 through 26 pounds. Does your sash's weight fall within that range?

Please keep in mind that the weight range information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.
A quick learner from Oxnard says:
Thank you for the quick reply!!!! Based on the information you just gave me, I'd say my 28" channel guide has a 19-002 top and 15-001 shoe. Please see attached pics. I'd like to order two as soon as possible. Thank you!!!
A customer submitted image of channel balance attachments.
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Tom from SWISCO responded:
Thanks for getting back to us! In that case, you were right. The Series 390 appears to be the best match to your balance.
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