I realized the site's photo coppression completely obliterated them on this group photo. So I did some zoom-ins the best I could. 

Here my conversion 50-70 Sharps.  Did researches at my best and, accordingly this gun is just very short of the very last Model 1859 being made, before serial numbers switched to the Model 1863. Three-grove rifling, stock replaced who knows when, generic condition still good. Extraction system does work flawlessly.                        

One more group photo. Not sure who these guys are. But the guy on the far right clearly has it. There's one guy in the middle, I can't tell for sure.

Group photo Co. C 321ST machine gun. Quite a number of the people sitting for this picture have the mg patch visible.

Sergeant James Burke Barton from Natchez, Mississippi. He was with Company D, 321st Machine Gun Battalion

Thanks for the reply! I have seen vintage pictures of troops that have been on a campaign for months, and the troops look quite rough. No bath, no clean clothes (they would often sleep in their clothes), and they slept on the ground, using their saddle as a pillow. They would also sleep with the horse's halter line wrapped around their hand, using the horse as a natural alarm if they were in dangerous territory. Not an easy life! Robert                                

I won myself an 82nd division uniform at auction, and it also has one of the machine gun patches. Though what seems to be the more common smaller type. I proceed to go on a photo hunting binge, and I found a good few. I will now post them here for people's futute reference.

great-looking Sharps carbine!, and in great condition.  IMO those converted to the centerfire round are among the coolest guns of that era.   Will post photos of mine.      

And this guy, with both mechanic and gunner's mate patches

I believe this fellow is coastal artillery, observer. Really crisp Studio photo. I was looking for photos of something completely different. Came across this one.