Help me choose what part to purchase

Question

The block and tackle is marked bsi 1830. The window label says series 4200 h-lc30-54x90. The string has broken in 2 windows and the other windows don't slide easily.

Bob · Accepted Answer

Thanks for posting. See the S380-19 or S385-19. The only difference between these two channel 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 1830.

Comparison of the S378, S380 and S385 balance shoes.