Help identify this part?

Thanks for writing in. This looks like either an S380-27 or S385-27. The only difference between these two channel balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement. See the diagram below for reference. Compare both with your old balance to see what matches best. In either case, for a new stamp option go with 2650.

Comparison of the S378, S380 and S385 balance shoes.

No, the stamp option is basically what determines how strong the spring is. Your old stamp was "26 5," which is an older rating system that you don't see used much anymore. Our stamp, "2650," is the same thing, its just a more modern way to print it on the metal.