@ E'dollo
RTO means Radio Telephone Operator, the guys who call in airstrikes air support or heli extractions. They carry the AN/PRC-77 Portable Radio that the SF guy in front of the cover has. Taken from wikipedia: "The AN/PRC 77 entered service in 1968 during the Vietnam War as an upgrade to the earlier AN/PRC 25."
And the ALICE backpacks are Rucksacks that MANNYYYYYY of the soldiers in vietnam had. Here are some pictures:
http://www.infobarrel.com/media/image/3793.jpg
http://west.loadup.com/images/large/11103.jpg
http://www.military-backpacks.com/im...molle-pack.jpg
Thanks to the sites for the Pictures.