That's interesting. I had the old style ROC, which I was told was valid for life. A couple of years ago I wanted to add on the satcom and DSC to it so did a 2 (?) day course and took the test, was issued with the LRC and a piece of paper telling me I needed it endorsed for gmdss if appropriate.
Well I tried to get it endorsed and and found out that the LRC is the replacement for the old ROC as I was lead to believe I was being examined for. AMERC were totally unhelpful and said that they had issued the right certificate and if I wanted an ROC or GOC I had to do the full course and exams again and that my original ROC is now no longer valid.
Having read the syllabus on their website it is clear to me that I was examined for the ROC but as it was probably 6 or 7 years ago I have no come back on anyone