mlschultz pretty much got it right. Brass tags are never used on Ford products. They identify assets for inventory and tax purposes. Notice that these tags are heavy duty, they don't have high numbers and they are not meant to be removed, ever. They are normally not screwed in place but riveted using 1/8" twist rivets that are pounded in. That's why you see the mounting holes are dimpled. They are hard to pry off by design.
I'm also retired from Ford Motor but in Dearborn. Dearborn Assembly Plant NEVER put one on a Thunderbird, Mustang, Cougar, Maverick or Comet.
Rotation Forms and VINs identify every product Ford made. The Quality Control Dept. and Scheduling both used these as identification. All tests and materials go through 'Quality' and all rotation changes go through 'Scheduling'.
Company-owned (corporate vehicles) were also identified by their 'unique to Ford' license plate numbers. WHQ is only two miles from The Rouge. The basement has a car wash and gas pumps. No money changes hands. The attendant simply notes the corporate (pool car) license number and charges the appropriate dept. There are thousands of pool cars. - Dave