Andy, there are likely more tint variations of Black than any other color. The Model T colors largely used Gilsonite to tint with until DeVilbiss pioneered spray gun technology in the mid-twenties and Ford started using alkyd enamels. Since the pigments back then were muddy, in all likelihood, the original Black on your Model A would not have had the depth that we see today in modern enamels & urethanes, and it would have been a very "muddy" Black. Probably the closest thing to that today would be PPG's DCC9700, ...however many people that see it do not like it as well as DCC9300 or DuPont's 'Pitch Black'. If you are trying to match colors on an old or original finish, I suggest you find a paint store that has a new paint spectrophotometer that can mix tints & reflectivity. Even then you will be required to play with the formula somewhat.
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