32 inch, 3140 stamp on rail

Question

I'm not completely sure which balance spring model would be an exact fit. The string on the pulley assembly snapped in half and I'd like to replace both sides.

Bob · Accepted Answer

Hey there. This looks like either the S380-32 or S385-32. The only difference between these two balances is the 'depth' of the bottom nylon shoe, or the 'heel-to-toe' measurement. See below. Measure your old balance's shoe depth to see what matches best. For a stamp option choose 3140.

Comparison of the S378, S380 and S385 balance shoes.