Most Carter ball and ball, or BB, carburetors have the numbers stamped on the air horn, but other models can be in various locations, such as on brass or metal tags or stamped on the flange. Some older models came with cardboard tags only and are very hard to identify.
The Carburetor Shop and The Carburetor Doctor have descriptions by year, make and model – some with photographs – to help identify Carter carburetors. Mike's Carburetor Parts has free manuals on all Carter model years and design styles that include diagrams of ID locations and parts ID numbers. The Carburetor Doctor and Mike's Carburetor Parts also have rebuild kits available for most Carter models.