That's a question for the people at Dean. Most likely they will tell you that it is just they way they label their bass guitars to tell them apart. Just like BOSS labels their guitar effects pedals. There is the Boss GT-10, the BOSS ME-70, the BOSS ME-20, etc. It's just sort of like a stock number or unit number and while the letters may actually stand for something for instance the BOSS VE-20 probably stands for Vocal Effect and the GT might stand for guitar. It's just an acronym Dean uses to distinguish between their different bass guitars. EAB could stand for Electric/Acoustic Bass Or perhaps the E stands for something else if its a straight acoustic bass guitar. I would guess that C5 might indicate a 5-string bass. I have an Ibanez SR505 bass. I have no idea what the SR stands for. The SR500 is a 4-string bass and the 505 is a 5-sting bass. So go figure. If you really want to know, call Dean customer service.