Non-tilt balance replacement

Hello. Have a look at both our S380-19 and S385-19 channel balances. These look very similar to your balance. The only difference between these two balances is the 'depth' measurement of the bottom balance shoe. You will need to measure the depth of your bottom shoe, the way it is shown in the diagram below, to determine which of the two balances is the better match. If I zoom in on your photo, I believe I can read "18 4" for the stamping. Could you confirm? If so, then whichever one chosen will go with an 1840 option that supports a sash weight of 14-17 pounds. 

Alternate view of 15-004