Interesting. It seems Hoover was in the automotive business but not making seats. They currently have a warehouse in Washington, southern IN, near my birth place. I never heard of them before today. From their website:
1913 Hoover Steel Ball Company was founded by Leander J. Hoover in Ann Arbor, MI.
1924 Imperial Bearings Company was acquired.
1936 Name was changed to Hoover Ball and Bearing Company.
1955 Merged with Universal Die Casting and Manufacturing Corporation.
1958 Acquired Strom Steel Ball Company and the Coolidge Corporation
1959 Ball Operations moved to Erwin, Tennessee.
1972 Created Joint Venture in North America with NSK.
1975 Entire Interest in Joint Venture was sold to NSK
Green id tag? 
I have never seen or heard of this tag before, but, I seriously doubt that the Hoover Ball and Bearing Co. had anything to do with the manufacture of the seats. Was this actually attached to the seat, or just kind of hanging around underneath it? 
) they didn't assemble the seats, or do the upholstery work. That kind of looks like something that someone was supposed to remove during the assembly phase, as in, the inspector checked the springs before Ford got them, the tag was there during assembly, so that Ford would know who to chew out if the springs turned out to be defective somehow, and then they were probably supposed to remove those tags. I do know that I've pulled a whole bunch of back seats out of Mustangs, and I've never seen one of those before. My little theory is just an educated guess, and could be just as wrong as wrong can be. 
