As far as I know, the Minkus Master was always sold new as a single volume album. I do not know when it was last available new. Attempts to get any information out of Amos Press have gone unanswered. Finding one used in good condition would be your best bet. I'd love to find a version from the early to mid-1950s, which could then be combined with the parts available from Amos to bring it into the 1970s.
About a year ago I picked up a 1965 edition with pages into 1964. Luckily it was lightly used (a few hundred stamps hinged into it) and complete. It contained spaces for just over 60K stamps, with the vast majority (96.2%) of spaces identifiable via Minkus number and/or an illustrated cut. I plan to use it as a checklist for building a side collection with my duplicates.
Depending on your goals, it might be easier to buy the Supreme Global which is available new from Amos. You'll get better coverage than the corresponding date range for the Scott International on decent paper. Yes, there will be editorial idiosyncrasies but you'll find that with any album you choose. That's the nature of the beast.
Whichever way you ultimately go, best of luck.

Dale