Channel balance 27" non tilt window

Thanks for posting. That stamp actually isn't an identifier; it just tells us the strength of the balance. Can you send us photos of the nylon attachments? That should help narrow things down. Also, can you send us photos of the 'guts' or underbelly of the metal channel? Some balances from the west coast have a special configuration we need to account for. Once we confirm everything we should be able to help from there. 

Thanks for getting back to me. This looks like either an S380-27 or S385-27 Channel Balance. 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 2630.

Comparison of the S378, S380 and S385 balance shoes.