It was actually a fluke accident that found Hal Shelton rounding the corner on 17th and walking into "Capt" Jeppesen on the streets of Denver, after WW2. After a some chit chat Jeppesen asked Shelton to stop by his offices and review some new maps he was having created that were done in an approach termed "natural-color relief map", and so he did. The end result was Jeppesen realized that Shelton could create superior base maps in this style and hired him to do so. This style might well be a by product of the air age as pilots began to notice the palette of the land beneath them and it communicated well the quality of land.
Here is the Jeppesen map for California that conveys the drastic variation of terrain throughout the state, as cultural info.
Condition is very good . Image size is approximately 38 x 31.25 (inches)