A very cool picture of a US Army Special Forces advisor in Vietnam. The interesting part is the M1A1 paratrooper carbine he is holding. You can see he has taped two 30 round magazines together for the gun and added a mag pouch to the stock that holds two 15 round mags. It would be interesting to know if this gun is an M2 that has the side folding stock added to it. Most M1s were brought up to M2 specs after WW2 , the magazine catch being one reason. The original did not do well with the extra weight of the newer 30 round mags.
The new Inland MFG currently makes a M1A1 carbine that is excellent. You can read my review of it from a few years ago linked below.