Very soon after I came to SDMB, I started a thread Those numbers in movie credits? on 06-26-2003, 01:02 PM. It got some action and some good information and I referred back to it yesterday while I was checking out some of the entries at Category:Film and video terminology From Wikipedia which makes for some fun trivia hunting.
Today I located this site which appears to be at least an interesting attempt to identify the movies with those elusive MPAA certificates, which now are in the 46,000 range.
If you have further details on this issue, please share. It appears to me that this whole numbering system – and even the provocation for its beginnings back in the 30’s – is mostly a relic of the old days. But it may be that I just haven’t located some better history on it.
Definitely some trivia for movie trivia fans!