The Zenith should have a round tag roughly the size of a dime, which is riveted on to the top casting. On the tag, there should be at least one set of stamped numbers oriented in a circle. There are probably two sets, an inner circle and an outer circle.

If two sets, the inner circle is the one that identified the carb.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop