I concur with Lew’s interpretation.
Since these manuals were compiled by Ordnance /Artificer officers and WO/s
from examples picked up or surrendered in the field, sometimes without packets, other times in full crates with all the relevant labels, there is still open for misinterpretaions and down-right mistakes in the final rendition.
One must remember, these guys were not collectors or students of ammunition, with our background knowledge of individual country rules about what was marked and when and how, as to ID of ammo.
And I doubt that they interrogated Enemy Ammo officers either to the extent that Phil Sharpe and his Team did in 1945-46 with the German ammo Makers…remember that PS was already an ammo “expert” before the war, and knew what questions to ask. I doubt ( knowing the British army system) that any of the Ammo Tech Officers had any knowledge outside of their narrow trade training in the Army, about ammo; and unless they had spent years at R^L or with Kynoch or Eley, would they have any clue what they were initially looking at.
But given all those problems, the descrptions in the 1942 Manual were pretty accurate, at least in General Terms. And given the details of both Air and Land use ammo, I would say that the manual was prepared on the basis of North African Capture ammo in total.
Just a misinterpretation of the significance or otherwise of Primer and neck colours as to Cartridge ID. ( a “British disease?”).
Interesting about the manual cover itself, it seems to have been the property of,(or Issued to) an Officer of the Dutch General Staff in Exile.