It means that the Merit Gold can only be earned once. So you serve once as a Nurse, you qualify for a Silver. You serve 3 times and that silver becomes a Gold. You may serve more times than three, but once you've earned the Gold you can not earn it again. :)
Well, I might just be special, but I tried to be a go-to person for my Ajah while I was Head. If at the very least they should be able to help direct questions. :o
As have many people! Collecting them takes.. a lot of time. Verifying can take even longer. Serenla just hired on and brought on people to make lists. Typically I've seen them given out at Anni and FB (or around those times). Was there a specific reason your asking? (Like that extra bond?) If...