15 1 FS caldwell

Thanks for posting! Were you looking for a replacement channel balance? If so, I'm afraid that this stamp doesn't tell us much. It only indicates the calibration of the spring.

In order to identify your Series, we'll need to see a clear picture of the top and bottom nylon fitting. That will allow us to match up the combination of fittings to something in our inventory.

Please make sure that your pictures are as clear as possible and that the hardware shown is whole and undamaged. It's very difficult to ID damaged hardware.

Perfect, these are exactly what I need to see. I was able to narrow it down to two possible replacement balances: either our S390-16 or S351-16. The only difference between these two assemblies is the depth of the bottom fitting, so you'll have to measure yours to confirm the better choice between them. 

Regardless of which one you go with, I'd also recommend the 1510 stamp option when prompted.