It's very Melior-like, but it's not Melior. Renault is also similar. I suspect they were custom designed for the ratings board when they were introduced in the late 1960s. This poster, which shows all of them together, seems to support this. The ratings that were added later--NC-17 and the 13 in PG-13--don't match the style. In the early years of the system, there was also X, and, for a short time, M and GP.
Wow, they didn't even bother to use the same font for the "13" and the "NC-17"�the "13" looks Korinna-ish, and the NC-17 Palatino-ish, but they don't seem to match digital versions exactly.
As for the other fonts: RESTRICTED is Helvetica Black, but I don't know about the "UNDER 17...". Superficially it looks like Alternate Gothic or Trade Gothic Bold, but the Q and R clearly don't match those. The only face I know that combines that kind of Q with that kind of R is Folio, but I can't seem to find a weight of Folio that matches that sample.
Univers Condensed has the wrong Q but otherwise gives you a pretty good match.
Captured from web.archive.org on 16 May 2005. view this capture