The GB models are, I believe, made in Indonesia, and are of cheaper construction (cabinet/soundboard/strings/pinblock) and design (no duplex scaling, no sostenuto pedal (it acts as a damper for the bass notes only), tackier key surfaces and is harder (physically) to tune due to the position of the pegs, no sliding music rack. It's a budget model and they have undertaken a lot of shortcuts to get it to that point. The C2 is part of their midrange, and is made in Japan, and has pretty much everything working/in place as it should be. That extra foot makes a difference, too. More than you might think. If the used one is in good condition, as your tech appears to indicate, it's a MUCH better buy.