Primer Marks Explained

I did not know this.
TSgt David L., PVT Mark Zehner
SGT James Murphy, CPT Jack Durish,
PO3 Bob McCord, LTC Laura Wickett,
SGT (Join to see), COL Mikel J. Burroughs,
SPC Gary Welch, SGT Mark Anderson,
CPL Douglas Chrysler, Maj Marty Hogan,
1SG Steven Imerman, SGT Gregory Lawritson,
MSgt Robert "Rock" Aldi, PO1 John Johnson,
MSgt David Hoffman, SSG Michael Noll,
SPC Nancy Greene, SSgt Terry P.