Caldwell window balance

Thanks for posting. Please confirm the metal channel length--do not include the nylon fittings on both ends in this measurement. Typically a balance with a stamp beginning with '17-' would be 18" long. Let us know if your balance is indeed 17", as that would be irregular. 

If the balance is in fact 18" as the stamp suggests, then this looks like either an S380-18 or S385-18, the difference between these two balances being the depth of the bottom nylon shoe, as shown below. You say the depth of your old balance's shoe is 1-3/16". The greatest depth on a wing shoe like this that we offer is 1-3/32", which is what is on the Series 385. Please double-check your shoe's depth. If it's in fact 1-3/32", then you have a Series 385. Assuming the channel is 18" long, it's the S385-18 with a stamp option of 1740. Let me know if you have further questions.

Comparison of the S378, S380 and S385 balance shoes.