Thanks Terry - all good info to know.
I can add (or muddy the waters?) to the markings info with the comment that, sometime after the diagram in Rob's post, both the USA and Australia (so I think it must be a NATO standard?) included a broad yellow band around the projectile, just below the shoulder. My US diagram is dated in the 1990s, and the images I have of Australian manufactured 105mm How HE ammunition show they were manufactured in the early 1990s. I took the images on the gunline during a live shoot in 2008. The howitzers were L118 Hamel.
I also looked at some period images on the AWM website, and this one:
https://www.awm.gov.au/collection/C318682
taken in August 1969 shows an M1 projectile with a light coloured band about to be loaded into an M2A2.
And this one, but date of manufacture unknown:
https://www.awm.gov.au/collection/C1142179
But this one in 1967 does not:
https://www.awm.gov.au/collection/C314824
I should also add that all 105 H ammunition fired by Australian gunners in South Vietnam was US supplied, not Australian.
Maybe it will depend on what time period is being represented?
Mike