Photos A hard day at the office...

[NebrHogger]

From the insignia, I'm guessing this to be around 1966 or so.

 

[Fish&Chips]

Good guess! I found a description here:

The strain of battle for Dong Xoai is shown on the face of U.S. Army Sgt. Philip Fink, an advisor to the 52nd Vietnamese Ranger battalion, shown June 12, 1965. The unit bore the brunt of recapturing the jungle outpost from the Viet Cong. (AP Photo/Steve Stibbens) - source: blogs.denverpost.com​