I would like some opinions here, I have attached here a partial 29 Dodge tools list, I have all three versions of this book printed May Sept Nov of 1929. What sizes would the wrench openings be if measured across the flats if I am to assume that this little ditty ..................In the United States prior to 1929 the sizes stamped on wrenches usually referred to the diameter of the bolt not the actual opening size. Thus a wrench stamped ½ U. S. would actually have a 7/8" wrench opening size as a nut for a ½" diameter U. S. Standard bolt would measure 13/16" across the flats and allowing for 1/16 clearance would require a 7/8" wrench opening. .............pertained to my wrenches and since they are unmarked on sizes that whomever published these tool lists were still using the old method of sizing up wrenches in that they considered the actual sizes of the bolts.
My eyes might be younger than some of you and I can barely read that toollist so the sizes are as follows
#1 3/8 ....7/16
#2 1/2.....9/16
#3 5/8.....3/4
#4  15/16 ....1 1/8

This is a more complicated question, it is not just the Bolt standards markings, SAE is also just coming into play at that time.
My offhand guess would be that they would be SAE sizes, because the SAE sizes were developed based mostly on what the auto industry was already using, eg US medium weight hardware.

[cheat, multiply bolt shank (stated size) x 1.5 to get head size, only for SAE, only for moderate sizes]

so #2 (1/2x9/16) should measure .750 x .844

Thanks again