This is generally correct, but a mate 500/1600 with at least one year experience as OICNW on vessels over 200 GRT can also sign. It's not in a NVIC, it's in CG-543 policy letter 11-07 (see para. 8 on page 3). http://www.uscg.mil/nmc/announcements/pdfs/CG-543%20Policy%20Letter%2011-07.pdf
Thats what I initially thought but I heard repeatedly it was a lawsuit. (In a way it is kind of like "suing" the nmc except the "judge" is uscg hq...)
REPLY I believe that is called an "Administrative Appeal" before an USCG ALJ (Administrative Law Judge).
So there is no possibility of 1600 mate to 3rd mate while working as mate on an ATB that is combined unlimited tonnage?