Michael, I checked both the online server and my own local archive collection and I can't find any reference to the previous 4 books in that early series. Perhaps it was a one-off contribution by someone.
However, that Book 5 mentions it was gleaned from a summer 1986 weekend workshop given by Tom Brohamer and Howard Sartin. We do have a later 1990 audio series workshop by Tom Brohamer and it would surprise me if Tom's basics, as recapped at the beginning of that Book 5, had changed much from 1986 - 1990. Thus, you would undoubtedly benefit from listening to that audio seminar and following in the accompanying PD of teh workbook for it. Here:
http://www.paceandcap.com/forums/showthread.php?t=6095
That said, and not trying to dissuade you from your forensic or archeological research into Sartin Methodology 'first principles' or its early evolution -- much of the early stuff is either insufficient to win in today's world of much greater knowledge, software automation and dissemination of original 'great ideas' (many of them originating from the Sartin Methodology), or still works but everyone else knows about it and it pays too little, much less than what made it valuable when it was new.
We advise newcomers to start their investigation of underlying principles with Follow Up Issue #70 and onwards where Howard starts to discuss the principles of Velocity relative to Deceleration (aka V/DC) and illustrate them with early versions of what became Validator which became RDSS.
I know you are not a newcomer (indeed one of the earliest members!) but perhaps a returning enthusiast seeking a broad understanding of the most important ideas of the Methodology? Presuming so, and presuming you feel the leisure to study and gain deep knowledge, the above references will serve you well. But so will posts by modern practitioners and explainers of their process such as (and not limited to): For The Lead, Mitch44, Bill Lyster, Bill V, rmath, Lt1, rdiam on betting, perhaps myself from time to time. And others.
Good luck in all your research.
Ted