Replacement springs BSI 27 5 RH

Thanks for posting. This looks like either the S380-28 or S385-28 Channel Balance. The only difference between these two balances is the 'depth' of the bottom nylon shoe. See below. Measure your old balance's shoe depth to see what matches best.

Comparison of the S378, S380 and S385 balance shoes.

You then have to choose a stamp option, which reflects the strength of the balance. In your case choose 2750.