Answer:
For the 1955 Ford passenger cars produced in the USA, the data plate is best defined as being the metal tag riveted to the "dogleg" below the A-pillar of the car. Usually made on a thin gauge aluminum, they are embossed with the vehicle's identification number, (VIN) on the top line, which vehicle specific data is entered into the lower line. This includes the body style, original paint color(s), interior trim scheme, and "production code" which includes the date of scheduled production, plus other information.
Phil Skinner
Collector Car Market Editor
Kelley Blue Book