WWII Marine info

[intrepid]

Does anyone know of a website where I could enter the name of my uncle (Guy Franklin Robinson), who was killed on Iwo Jima and obtain any information regarding his activities while serving?  I'm sure if I was back in the states I could visit the National Archives in Washington and find a little more.  He served with the 4th Marine Division.  Searching the normal sites on the internet I was able to learn about his division and whereabouts but that is about it.  I know it would be a long shot at this point to locate a marine that may have knew him, most have passed by now.  We still have the Western Union telegram my grandmother received advising of his death.  Also a letter from either his captain or Chaplin that arrived a few days after the telegram.  Would have loved to research that person years ago.  At the time he was killed his oldest brother had been serving in Europe with the army and just transferred to Iceland.  His second oldest brother was in the Army Air Corp several areas in Asia.  On a refueling stop at Iwo Jima just before the war ended he was able to visit the War Cemetery .  He always had a camera and took a lot of photos.  We have many from the the cemetery and the tombstone.  Below is one of the photos of his tombstone at the Iwo Jima War Cemetery.  What is the number above USMC?  Dog Tag number?