18 pounder cartridge case mark variations?

[Darkman]

Could someone please explain the differences in the marks for 18 pounder cases? I have a number of 18 pounder and ammunition handbooks, but none detail the mark variations for cases. There are a couple of obvious changes such as mouth crimps for Mk I and weight (presumably wall thickness), but other than that I'm stumped.
There are Mks I, I*, I**, II, III & IV that I have, or have seen.

Thanks,

Graeme

 

[Darkman]

Whoops! I'm getting confused. Wall thickness and weight are projectile variations not cases.

Mk 1 case has 4 x segmented mouth crimps, Mk II obviously has no mouth crimps and is coned over to match the driveband profile. Mk I* is a Mk I case modified/reworked to Mk II. Mk I** is a a Mk I case modified/reworked to Mk III. So what are the Mk III and Mk IV variations?

 

[Darkman]

Still keen to find out the mark differences. I can't find any information.

 

[Darkman]

I recently saw a mk II* case, but still no closer to understanding the differences between marks.