Having just checked several different eras of 'Mini Owner Handbooks' that I have, they all seem to have a similar pattern of number codes on the back pages. The 1/60 part in your Workshop manual seems to directly tie up as the month/year of printing in my BMC/BL Handbooks. Some of the other numbers sound about right for a print run number. However the number which seems about right for a print run does not always seem to be in brackets and numbers like 3m, etc seem far too high for a print run number if m was to represent a million? Also bearing in mind frequent changes and updates I am sure manuals and handbooks would usually be printed in batches of a few thousand at a time.