Based on the article references by @Matthieu, I ordered 2 8gig RAM sticks from Other World Computer and have successfully installed 16 gigs of RAM on my 2012 MacBook Pro. The System Info panel does display 2 slots as containing 8 gigs each for a total of 16 gigs.
If you are ordering RAM please ensure that the voltage spec matches the newer model's 1.35V instead of 1.5V from the previous (2011) version. I do have 2 sticks of PC 133 DDR3 but the voltage requirement is 1.5. This could cause issues like some users have reported.