16 4 RY Caldwell or 16 3 AW 3MC 4 (?)

Hello there!

With this combination of attachments, you could have either an S380-17 or S385-17 channel balance. You’ll need to measure as shown below. The Series 380 has a 1" bottom attachment, and the Series 385 has a 1-3/32" attachment. For the balance marked "16 4", you'll need a stamp option of 1640. As for the other balance, it looks to be marked "16 3", but it's hard to tell. If you're unsure, you can always weigh your sash on a scale to determine the appropriate stamp option.

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