I own two USMC marked pouches.they differ from Army pouches in the shape of the flap/body, lack of the large US printed on the flap, are a different shade of light green, and sometimes are a mustard brown color closer to WW1 web gear. It's not unusual to see photos of Marines on Iwo, and Okinawa with both Army and USMC pouches.some times on the same guy. The only thing I have to say about the USMC pouches, is that the Marines seemed to use "regular" Army pouches just as often (if not more) than their own design.probably due to logistics, and the sheer number of Army style stock pouches produced. Both of which I have little interest or much knowledge about. Then there are also USMC pouches, and 30 rd mag pouches. Not until post war occupation duty or Korea have I seen these pouches used in numbers. I have seen very very few photos of these pouches used in WW2.the overwhelming majority seems to favor the earlier pouch. All the 1945 and 50's dated ones I have are the dark OD. They are mostly all dark OD, with a few light OD examples dated mostly 1943 and 44, as well as pouches that have both colors on them. I have examples of this pouch dated 1943, 1944, 1945, and with 1950's dates. and all late war produced pouches were the belt only combo pouch. These, for a short time were made concurrently with the earlier "stock" pouches in late 1943/early 1944, and then it seems the early pouch was discontinued from mfg. There are also WW2 production "combo" belt only pouches the hold either two 15 round carbine mags, or two 8 round Garand clips. I have examples of these pouches dated 1942, and 1943, both in light and dark od, and some with a mix of both colors used on the same pouch. The light OD/khaki two pocket mag pouch with the snap on the back ,often called the "stock pouch" by collectors, because it will fit on the butt stock (be careful not to ding the stock up with the snap), was the most common pouch used during WW2. WW2 production slings will also have "C" shaped tabs on the sling ends, and post war slings ill have solid body "D" shaped tabs. On a post war rebuild carbine, any USGI sling is fine. Post war slings seem to be all the dark OD color. Dark OD slings (od#7) would have been seen from late 1944 on, maybe a few earlier, but the light od/khaki slings (od#3) were far more common for almost the entirety of WW2.