I am too lazy to Google it for you, but I would suggest a search term of "Holley 7806". I am sure someone has posted it somewhere online. As for my best guess, I would say it is a 600 CFM emissions Holley. These were built as stock replacement carbs during the 1970's and 1980's. Typically, they were used by people who did not understand Quadrajets, or were tired of some of the more troublesome smog carb variants of the period. These would include the Motorcraft Variable venturi and 4 barrel carbs (all Motorcraft carbs were rubbish!), the Carter Thermoquad, and possibly also the Carter AVS. Applications were widely varied, but most used the 4150 (4160?) architecture like the old stand by, the List# 1850 600 CFM universal carb. Ford also used holley 4 barrel carbs in the 1980's on 302's in Mustangs, 351W police LTD's, and some 302/351W large trucks and vans. However, the Ford Holleys have a vapor recovery line on the float bowl which I do not see in the pictures you provided, so it is not one of those unless someone changed the bowls. The final possibility is that it could be a small carb intended for a tunnel ram or other dual quad configuration. These were typically either 390 or 450 CFM, and were also sometimes used on inline sixes with Clifford or Offenhauser 4 barrel intakes.