Pete you have me looking now. I did find http://reject-bastids.proboards.com/thread/531/missouri-meerschaum-logo-timeline
This is the reply from MM when asked about records of labeling,
Unfortunately, nothing has been kept over the years to give us a timeline on the bottom labels. Most of the old catalogs don't show the bottom of the pipes so there really isn't a way to tell exactly how old a pipe is by the label on the bottom.