I may have been wrong about the last year 32/33's were made.  Late 70's may be correct.  I was purchasing 33 parts direct from Teletype until about 1985 I think. 

 

See pic for printer serial # location.  There should be 6 digits. I have seen 800, 000 numbers I believe. 

 

Best regards,

 

Wayne

KB1FDW