I believe this to be an experimental Holley carburetor from the early development of the Model A in 1927.
I bought this carburetor from a man who said he got it from another person who got it at one of the Henry Ford Museum & Greenfield Village property dispersal auctions in the late 1980's.
It is a fact that a number of rare Model T and A items got sold at that auction including such things as an experimental X-8 engine.
It makes some sense that this may be a Holley prototype or development carburetor because in 1927 Harold Hicks of Ford Aviation was tasked to get the 40 horsepower out of the Model A engine on the dynamometer as Henry demanded, and he was working closely with Zenith-Detroit on an improved carburetor.
George Holley's company had previously had the inside track with Henry Ford supplying carburetors, but was forced to compete to save the business. This may have been a failed attempt at a Holley design for the A.
The familiar Zenith carburetor design ultimately prevailed in the testing, but Holley was able to supply many carburetors to Ford under license from Zenith. This was due to the fact that Zenith was not set up for high volume automotive production, whereas Holley had the capacity to supply Ford volumes.
This carb is somewhat similar to some Model T carburetors, but has the distinctive Model A choke control and gas adjusting valve. It is marked as a Model 440, but I do not believe it was commercially produced.
I have never seen or heard of another carburetor like this one, and I cannot find any era advertisements for it in magazines such as Ford Dealer & Service Field, Motor, and Auto Digest of the era.
This carburetor is almost new and shows no wear. It is a very high quality of manufacture and all the parts appear much higher precision than a production Model A carburetor.
If any reader has better information on this carburetor, I would appreciate hearing from you.