How to tell size of carb

[EARLY B]

How can i tell the size of this carb the air horn is gone and no list number found?

 

[33 IMP]

Pull it off the engine. Measure the size of the throttle blades. TRY to estimate the venturi size (more easily accurately measured by removing the throttle plate. I wouldn't bother).
Then take your measurements/ guesstimate to Holleys web site.
(750 is the most common double pumper. Street driven 440, a 750 would be a good choice).
Edit There are also numbers on the metering blocks. They may or may not help.

 

[1STMP]

https://www.holley.com/blog/post/how_to_identify_your_holley_or_demon_carburetor/

 

[Geoff 2]

Rough idea: 1 9/16" t/bores 600 cfm
1 11/16" bores 750 or more cfm.