That's the west coast promo pressed at Monarch and denoted by the 'MO' at the end of the catalogue number.
After 1966 all Atlantic distributed records used this system to denote which of the following plants their 45s were pressed at.
PL = Plastic Products, Memphis TN
SP = Specialty, Olyphant PA
MO = Monarch, Los Angels CA
AM = ARP, Owosso MI
CO = Columbia, Terra Haute IN
These are the main ones and there are a couple of others but I can't recall them off the top of my head.