I forgot to mention that early Quality H.M.C. carbines also have this front ring comma up to serial number 1621877. QHMC carbine 1633386 and beyond do not have the comma. Somewhere inside this range of serial numbers is where the comma went away. If you have one or know someone who has a QHMC carbine within this serial number range please let me know and I'll add it to my spread sheet and narrow the gap. All NPM 'U' and all UN-QUALITY receivers that I've seen have the comma on the front ring. Newsletter 380-19 has a short blurb on this "comma question".
QHMC 1581622
