Yeah, it's not an exact match, but it's as close as I got at this point in time with the information available and my limited capacity to understand...
The packing pieces were standard on all boxes. I've got a 1940 box still with the original packing pieces (with gas check disc holes) and three Navy...
I think I might have stumbled onto a partial solution - I found this listing on a South-African auction site of that is alleged to be a shell casing...
Just got my hands on a WW2 Mill grenade box 'for Naval use only' missing lid, partitions and 4 post separators. Looking inside where the grenades are...