Mostly right, but T = Temperance, which literally means 'abstinence from alcoholic drink' but I knew the odd two or three who chose 'T' purely because they disliked the daily rum ration but had no objection to drinking pretty much any other alcoholic beverage.
IIRC the T rating's 'perk' for not drawing their tot was 3d or 4d per day in lieu and had remained at that amount for many years... Barons, every one of 'em, eh?
The Tot was the most stable currency in the world
Some people would do a duty for you if you gave them a tot.
Need the chippy to make you a ships crest, give him a tot.
From sippers to gulpers to sandy bottoms each was part of the RN currency