Are there some other letters that you didnt show? In the posted letter he says the hole is the size of a silver dollar, but he doesnt say anything about the size of the fragment. I think it is a bullet because if you look at the actual entry point, the hole seems very regular, as you see with bullet hits, and it also seems to be the right size. The much larger hole we see further on was caused by the metal being bent back, it doesnt correspond to the size of the projectile. In any case, the projectile continued  forward, tried unsuccessfully to exit the helmet, then travelled between the shell and liner, and exited at the front of the liner. Since the projectile followed this course, it could not have caused a wound to the soldier's scalp at the area of the entry hole. These are just my observations.

Incredible find, and with the combination of laundry number and officer rank, it should be researchable. 

Here's a vet owned bring back I saw on Facebook years ago. He wore grenade rings in his helmet band.   

Here's another GI armed with the FN FAL Rifle, here while trialing the de Lackner HZ-1 Aerocycle.

Thank you. These are currently listed on ebay. I thought maybe the gold color was the lighting or silver tarnish as the back is dark. Seller also has a bombadier wing that looks gold in color.

Hello. I am going to an event as a Korean War infantryman. Could I get opinions on my uniform before I go? Anything to change? It’s a M47 uniform with M48 boots. 

Cool find, looks Japanese made too 

Curious indeed. See the 510th Tank Battalion was simply the old 10th Cavalry downsized and redesignated, see the 10th Cav's Buffalo Pocket Patch, it was formed in October 1950 and was at Camp Polk Louisiana, sent to Germany, around late 1952 where it was a separate Tank Battalion under the 19th Armor Group, and later the 4th Armor Group 7th Army, though by that time it was no longer an all Black unit. I can find nowhere where the 510th Tk Bn was assigned or attached to the 3rd Armored Division in Germany. So generally speaking, a 7th Army patch should be worn on the shoulder, while the 510 Triangle worn over the U.S. ARMY Tape, thus the curiosity.

Best part about that gap between grips and cross guard is that it only takes a quick glance to see how the cross guard is fixed in place eg. bent U shaped hoop or welded as some of the later made ones are.

They look ok to me although somewhat a crude strike. They match this one pictured on my website https://www.ww2wings.com/wings/usaaf/flightsurgeon/presleyclutchflightsurgeon.shtml I'll copy the photos into the post as well. Main difference is the one on my site is not sterling marked and is gold on the front and the back. Most of the gold flight surgeon wings are gold on both sides. Yours is a bit odd in that regard. The gold flight surgeon and flight nurse wings were not in use for very long before they were reverted to silver like the rest of the Army Air Force wings. I would place these in the WW2 timeframe but as Patrick has pointed out in other posts some of these wings continued to be made after the war. There were no hard cutoff dates in August of 1945. The gold would definitely be WW2 timeframe. Maker is not known at least not that I'm aware of.