A real deal pic, but not attached the way we typically do around here. It appears to be the only pic with a GP sling I have saved.
FWIW from a historical perspective: I just looked through 121 Vietnam pics saved in my CAR15 folder and most had either M1 or web 1918 BAR slings (hard to tell the difference in the pics, most of the SF and High Speed types were using these also), some had what appeared to be
rubber surgical tubing, some were parachute cord, others had unidentifiable improvised web slings, one guy had a length of G.I. rapelling rope.