Yes, if it is a Series 770 with a channel length of 28" the stamp will normally start with 28. Please reply with detailed photos of the current balance, perhaps you have a different balance series.
A contractor from Central Florida says:
August 10, 2010
Good Day,
I'm trying to replace a S770 balance and I'm confused. The overall meas. is 28", but there's a stamp of 27b on it ? Your help is appreciated.