I came across some additional information from the FUSA Medical Plan for Operation NEPTUNE and since I surmise that perhaps these are the items that we see in the photographs that have been posted on this thread:
(3)Special Units. Special units in waterproof containers will be carried ashore by enlisted Medical Department personnel for units indicated through D + 3, as follows
1 x unit per Inf Bn; Arty En; Chem Bn; Engr Bn; Ranger Bn.
2 x units per Coll Co, Division.
4 x units per Clr Co, Division.
6 x units per Med Bn (Engr Spec Brig).
Units will consist of approximately eight ( 8 ) small containers, which personnel may float ashore using the containers for buoyancy where required. Each unit will provide the following:
Dressings, First-Aid, Large (50 ea.)
Dressings, First-Aid, Small (50 ea.)
Gauze, Plain, Sterilized, (50 ea.)
Bandage, Gauze, 3-inch (50 ea.)
Sulfanilamide, Crystalline (10 pkg.)
Morphine, Tartrate, Syrettes (25 boxes)
Serum, Normal Human Plasma, Dried (7 pkg.)
Sulfadiazine, USP, 7.7 gr Tabs, 1000 (1 bottle)
Halazone, 1/10 gr Tabs, 100 (1 bottle)
Sterile Gauze Packet (impregnated with boric acid or vaseline) (1 ea.)
Unfortunately there was no illustration to accompany the above text, but I surmise that this is indeed the contents list for the containers seen in the photographs.