26 4 AS Caldwell balances

I'm afraid all I can determine from the stamp is that your balance will be 27" long and have a stamp of 2640. I see you were looking at our Series 380 channel balance. Does this Series match what you have? The only way to know for sure is to carefully compare the size of the nylon attachments to your own. Also, keep in mind that you only measure the metal channel when determining the length. I notice you went for our S380-28, which is a bit too long, if your stamp is any indication.