Some assemblies have ID marks stamped somewhere on the body. The BS series had numbers inked on the sides and those are mostly long gone. Ident is made usually by knowledge of the characteristics of particular assemblies and what models those assemblies were fitted to... there are small differences on carb assemblies that would otherwise look the same in other words that you can learn through experience.
wiredgeorge Motorcycle Carburetors
Mico TX
www.wgcarbs.com
Too many bikes to list!
