It is a "port" indeed. According to Mag-na-port:
"Mag-na-port offers a unique system of porting semi-automatics by using a trapezoidal port through the barrel and an oversized expansion vent through the slide to allow maximum dissipation without fouling. This process offers an alternative to shooters not wanting additonal weight or length from add on compensators.
Shooters using Mag-na-port's "autoporting" services do not experience the large flash of muzzle blast experienced with systems dumping larger volumes of gases through holes positioned across the center line. Law enforcement agencies and companies offering night sights have tested our porting service finding no increase in muzzle blast or night blindness attributed to our porting service."
The "ports" are roughly at 10:00 and 2:00.
I also custom ordered a pair of Gaboon Ebony (Black) grips from Esmeralda. (
http://www.esmeralda.cc/) Here they are in white:
Best wishes.