Alright guys. There is not necessary any relationship between railroad lettering and fonts.
A Font is a set of letters and other characters used by printers. These design sets were converted to electronic formats over the last few decades as the printing trade went from metal to electronic composition.
Lettering on railroad cars in the past came from the professional sign painters and then from the letters and numbers drafted by the railroad engineering department. While these may follow the general styles used in printing these would unique to themselves. The drawings prepared by the railroad engineering department would be converted into various kinds of stencils and pounce patterns for the railroad painters to use.
Some later railroad lettering and paint styles were created by design firms that made use of existing print fonts. An example of this is the large "Santa Fe" applied to its diesels and cars -- this is the "Cooper Black" font.
Now because of the time period that the D&S developed their letter it may very well be based upon a font. But it could have been free-lanced by a design firm.
Brian Norden