It looks like some Road Series guitars got updates; nicer rosettes, purflings, fretboard inlays and better electrics. And they got numbers instead of those confusing letters. The DCRSG is now the GPC-13E and the 000rsg is now the 000-13E.
But don't think Martin is making it any easier to understand. The Road Series letters were confusing enough, now the RS guitars can be anything from a 10 to a 13. I guess it makes sense to them.
https://www.martinguitar.com/guitars/