The Murfin Map is odd. Notice that there are no soundings, no lines of magnetic declination, and the lat/lon grid is unusually dense for the scale. The Hawaiian chain is off of the piece of the map we see, but the Marianas are present. OTOH, the typefaces and place names are the same as 528. I can't work out the scale of the Murfin map, but it is in the neighborhood of 528.
Maybe the Murfin chart is a small piece of a much larger chart covering the whole Northern Pacific. Alternatively, maybe the Murfin map isn't a proper nautical chart at all, but a "plotting chart" or "planning chart," printed in quantity, and marked up for planning operations, or plotting radio bearings, or whatever.
If you search on "chart" in the Purdue Library, you will see several "meteorological plotting charts," each containing hand-drawn pressure isobars, etc to illustrate an individual forecast.
adr