Individual Progress Method (DJS)

I have a box set called Gregg Shorthand Individual Progress Method (Diamond Jubilee Series) which was published by McGraw Hill in 1972.  It came with two spiral-bound books (a theory presentation book and a reinforcement book for practicing what you learned in the first book), plus a Self-Check notepad and a "Gregg Official Shorthand Notebook".  It does NOT contain any tapes although the preface to the Presentation Book clearly states that the IPM consists of 5 items -- the 2 books above, the self-checks and two sets of tapes, one set for presentation and a second set for dictation.  Each set supposedly contains 20 cassettes each.
I'm just wondering if anyone has ever seen or heard of these tapes, especially the dictation ones which is what I'm most interested in.  I've checked occasionally on ebay and the like for anything like this but have never found it.  I have seen these "Text Kits in Continuing Education" that were published in 1965 that seem to come with floppy records, but I'm not sure if that's the same thing.  It's still DJS, but maybe the actual material is different from what I'm using?  I dunno.  I'm not sure if I should buy it or not.  I really like the format of the IPM and I don't want to switch tracks.  On the other hand, I'd really like to practice with "real" dictation audio.
Do these IPM cassette tapes really exist?  Does anyone know the title or how they were packaged so that I know what I should be searching for?  I assume they were sold separately from the IPM box set since there's no room in the box to hold that many cassettes.  If I can get the cassettes I will gladly burn some CDs or MP3 files for anyone who wants them.  Thanks a lot for any leads.
~ Kim

(by kimskim for everyone)