Channel Balance

I don't believe that's accurate, unfortunately. The Caldwell stamp you gave, "23 4 FK," indicates a metal channel length of 24", which eliminates the S385-23 as a potential replacement.

It's important to note that the stamp printed on your old balance is NOT a part number. All it tells you is how the spring is calibrated and, to a certain extent, how long the metal channel is. It's not otherwise used in identification.

I recommend watching the video below to get a better idea of what details you need to consider when identifying your balance.