Okay, book open in front of me. Other than the randomly pattern applied with a big brush and the elasticated cuffs, which we've already talked about, other features of the MkI Denison are -
- a half steel zip going to the base of the chest (sometimes converted to go full length),
- two internal pockets, four external pockets (with brass snaps),
- the 'ape tail' crotch flap sewn at the back and secured with brass snaps at the front (although these were sometimes removed by owners for comfort after the jump),
- the base colour is more yellowy and sandy than later Mks, due to its use in North Africa and Sicily.
I hope this helps. Of course, if it's dated 1942 on the sizing label, then it's definitely a MkI (or a fake MkI, in which case you're on your own).