I guess they just numbered cars anyway they liked as 5,000,000 is a coupe in the Bill Smith Museum.
I just noticed on the side of the car that it says that this was a dealer since 1903.
W. L. Hughson was one of Ford's first dealers. His "Reminiscences" is included with the collection of interviews conducted in the early to mid 1950's, now at Benson Library (The Henry Ford).
The online Reminiscences described below:
"W. L. Hughson met Henry Ford in 1902 at the Chicago Automobile Show and in 1903 became the first Ford dealer with the West Coast and Hawaii as his territory. He describes Ford at the Panama-Pacific Exposition, Ford expansion in the West, and Ford dealer policy 1903-1952."
The entire interview:
One excerpt, page 16, relates Mr. Hughson's recollection of the $5 workday. Historically, I believe both James Couzens and Henry Ford are credited with pushing for the dramatic pay raise. In his interview, W. L. Hughson believes it was Henry Ford's idea: