I recall the Legion of Decency too!  

  (My brothers would giggle when they published the  movie ratings,  and would seek out the (coveted 

 ) "C" categories, and try to sneak into movies with that rating!)  

Copied from Wikipedia on Google (below) --
- A: Morally unobjectionable
 
- B: Morally objectionable in part
 
- C: Condemned by the Legion of Decency
 
The 
A rating was subsequently divided:
- A-I: Suitable for all audiences
 
- A-II: Suitable for adults; later — after the introduction of A-III — suitable for adults and adolescents
 
- A-III: Suitable for adults only
 
- A-IV: For adults with reservations
 
In 1978, the 
B and 
C ratings were combined into a new 
O rating for "morally offensive" films.