Someone else commented that this is probably Operation Blue Bat, and I think that is correct. I seriously doubt this has anything to do with the 1983 mission.

It appears that those are definitely late 50's, early 60's uniforms. First, you can tell by the white undershirts. In the 80's, those wouldn't have been permitted, everything had to be olive drab.

Second, they would have M-16's in the 80's, these guys appear to be carrying M-1's.

Third, no nametags on the uniforms. Embroidered olive drab name tags were mandatory in the 80's, for the army anyway, one side had your last name above the pocket, and the other side had "US Army" above the pocket.

Fourth, the uniforms would probably be camo, not standard Olive Drab in the 80's. And what's with some of them wearing helmets and some wearing caps? I don't think any unit in the 80's would let that happen.

So 1958 looks correct to me.

As for the flag, it's just a guidon, so it's probably something to do with their history, like maybe this is a unit based in Mississippi or something. I think each unit would choose it's guidon based on it's unit history. Many just had their unit designation in block letters, but I'm sure that considerable leeway was given for a mission like this.