Pawel
there's a strap for the gas mask bag on the front of the coat, but none on the back... I'll not correct this one though, as on the rear the spot will be covered by the canteen. I'd like to ask one more question if I may - what can you tell me about that shoulder US flag patch? Such flag is not so often there, is it?
M17 mask carrer has two straps, both are the same width. One loops over the opposite hip, the other around the thigh. There's a pocket on the bottom left (looking at the front of the carrier) that's very rectangular, that contains the decontamination kit, which is in a hard(ish) vinyl/plastic container. So, the shape in the corner is quite distinct.
Prefered wear in 1990 was to snug the canteen to where it sat above the "notch" created by that decon pocket.
Amercian flags became a more common thing which in multinational deployments.
Byt rule they were menat to have the blue union to the front of the wearer, but supplies of those were limited, so, seeing them "backwards" (blue union to viewer's left) was some common. Usually they were "bright" but some subdued examples were in the field.
Barring matching an actual photo, I'd probably go bright. I'd probably render it "backwards" too, if only to tweak the experienced. (Marines probably sent LCpl Snuffy down to the PX/BX to go grab all the US flag patches available at the beginning of the deployment, to get everyone to local SOP, and would not be picky--and would be distracted by the cases of I.W.Harper.)
If I can find my M17, I get you some photos.