channel block & tackle window balance

Thanks for posting. I am confident we can help, but that stamp does not tell us your channel balance's identity, only its strength. This is important information, but to know the identity of your balance, we need the following details:

• Please send us pictures of the nylon attachments or fittings on both ends of the metal channel. The fittings used determine the kind of balance you have, or what we call the Series. 
• Tell us the length of the metal channel. Do not include the fittings on both ends in this measurement. 
• Finally, please confirm the first three numbers on your balance's stamp. I believe they read '26-4', but it's a bit tough to tell. Check the other balance from this window if you're unsure. 

From there we should be able to narrow this all down for you. 

These photos are perfect, thank you again. Based on what I see here, you have either our S380-27 or S385-27, depending on the depth of the bottom shoe. That's the only difference between them. I recommend measuring your shoe and referring to our dimensions to confirm the best match.

Comparison of the S378, S380 and S385 balance shoes.