I believe that the dial had the AM broadcast stations in three groups: East, Central and West, so it covered the major broadcasters across the country. The radio shown in post #1 seems to have the scale shifted upward, so the call letters of the Eastern stations are not seen. Only the locations of the Eastern stations can be seen. The scale was shifted when in Shortwave mode to reveal shortwave frequencies, call letters and cities of location of the major international shortwave broadcasters.
EDIT add pix showing East, Central and West markings:
Shortwave typical display:
jr