They searched you leaving Vietnam..confiscated anything like empty grenades, double edged blades (Montagnards spear heads for instance). Almost no trophies other than uniforms, helmets etc. made it back...at least for enlisted men and that included Special Forces. They tried to confiscate my Randall knife...the one I carried 40 years later in Afghanistan.
Made me think of my Randall which was confiscated during desert storm and had to be replace when I got home. I now have a bunch of Randalls, which like my Shotguns I only seem to use one of, a Model 10, 90% of the time.