One of the most exciting x-rays my dentist has taken for me (and its not a 7.62x51mm)! Brass case with nickel primer and red primer seal. Headstamp is REM-UMC 223. The first bullet has a green tip and milled cannlure. Both bullets are GM. I believe that this is one of the first .223 duplex cartridge loaded (Dave Hughes in The M16 Rifle and its Cartridges claims that less than 20 rounds were loaded in late 1962).