The Q (quicklock?) denotes that it has a plug-it cord, e.g. when festool changed the vecturo from a plug it cord to a normal cord, the name changed from VECTURO OS 400 EQ to VECTURO OS 400 E.
The C (cordless?) indeed means its battery powered, e.g. TS 55 REBQ vs TSC 55 REB
So a CARVEX PSC 420 EBQ does not exist, it's either a CARVEX PS 420 EBQ or a CARVEX PSC 420 EB, and since they mention Lithium Ion 18V, it's probably the latter, so the Q is just a typo I guess.
Unless you are getting a cool new prototype that can work on batteries and AC power like the ETSC 125 Li 3,1
![Eek! [eek]](https://www.festoolownersgroup.com/Smileys/default/eek.gif)