This may be of some interest. I have a copy of study done by Steve Madden on the production of the various Denison smocks. In the study is a copy of Specification NO. U/1095A issued 21.6.45. Below is an excerpt:
Drill No.4 Camouflaged, W.P. M.S.B. 1203
1. Material: The fabric shall be all cotton
3. Dye: The goods shall be thoroughly penetrated with vat dyestuffs to the shades and design of the standard pattern, and the dye equally fast.
Note: W.P. indicates waterproofed.
Schedule "A" mentions that the material is 28" wide