Well, notice how my belt is made up of 1 section of leather. The later additions are composed of 3 sections of leather divided by brass fastenings. I would argue your image Albert of the Mk1 maybe in fact a later variant. Again the Australian war memorial features an example of a mk2 belt. This example being shown on the following link: https://www.awm.gov.au/collection/REL/03159.001
Sadly i have yet to get hold of the official list of changes publication so i am reliant on the secondary sources such as the Australian war memorial website.
What i find rather unique to the mark 1 is that the rear hooks are held together a single leather backing. The mark 2's brass hooks are held together by a double leather backing. Sorry if this is confusing, its hard to explain.
I provide a quotation from the Australian war memorial website:
'In the Mark II belt the buckles were sewn within the double-thickness of leather at the centre back section.' If you look closely the below image will emphasize my point.
Notice how the rear straps are held together by studs and a single leather backing on the image below: