CORRECTION
This is not really Tim O'Neill but as Tim is the senior tanker to sign in it is only fair and just to use him as the typical example of a tank crew member.
Identifying features that clearly point out the tanker background of this hero follow:
1. Round Head - Formed through selective breeding to fit silly helmets worn by all tank crew members.
2. Hairy Face - As a result of constant immersion in diesel fuel and lubricating oil tankers find it impossible to shave.
3. Squinty Eyes - A direct result of long hours looking through vision blocks rather than opening a hatch to look outside.
4. Irregular Teeth - Attributed to opening beer bottles with the teeth; this seems in error as most tankers drink canned beer.
5. Fleshy Jowls - Fatty tissue and loose skin come from over eating while not exercising.
6. Lack of Visible Ears - Atrophy, they never listen.
7. Wide Nostrils - Wide fingers.
8. Muscular Upper Arms - A normal result of slamming hatches whenever loud noises are heard.

In all fairness that does not look like Tim at all. Here is the real Timothy O'Neill in a photo taken in 1987. And here is a little background on his life since Vietnam:
A 25-year career as an officer in the United States Army, including two years of combat in Viet Nam and 15 years as a member of the tenured faculty at West Point. Colonel O'Neill commanded tank and armored cavalry units, and served on squadron and brigade staffs. He was a member of the permanent faculty of the Department of Behavioral Sciences and Leadership at the U. S. Military Academy from 1976 to 1991.
Since retirement, Tim served as Vice President of Star Mountain, Inc., a Washington-area training company, and presently serves as President and Chief Operating Officer of MSG&S, Inc., which provides equipment, services, and training for antiterrorism and security for clients worldwide; he also plans and conducts training in techniques of military instruction for foreign elite military and law enforcement units.
Tim holds a bachelor's degree from The Citadel, the MA in College Teaching from the University of North Carolina, and the Ph.D. in Experimental Psychology and Neuroscience from the University of Virginia; he is a graduate of the Armed Forces Staff College, and is an adjunct lecturer for the Johns Hopkins University. He is author of two books (Shades of Gray, Viking Penguin Inc. and The Individuated Hobbit: Jung, Tolkien and the Archtypes of Middle-Earth, Houghton Mufflin Co.) and numerous articles and monographs on military and scientific topics.
Tim is Chairman of the 28th Regiment, Massachusetts Volunteer Infantry, and serves as first lieutenant. His great-grandfather served in Company C, 4th Tennessee Infantry and the First Foreign Battalion, C.S.A.