I think the ID number on the dropout probably indicates the 15th week of 1972, per Hummer's Gitane serial number thread.

I agree with getting rid of the plastic derailleur if you plan to clean it up and ride the bike, but be aware Simplex hangers are not the same as standard hangers from the later 1970s and 80s, so a conversion is not necessarily simple.

I also converted one of these to a single speed recently by redishing the rear wheel and moving the big chain ring to the inside of the crank (heresy!).

Or if you plan to just hang it up somewhere and admire its agedness, be sure to give it a good shake first so bits of gunk don't fall off and land in your soup.