I said before they should check the private archives for those tapes! There's a wealth of stuff inthere.
Who knows people actually do find them Marantz amplifiers there, though that's not too likely as they were part of rack equipment. The only gaps to fill in that research are how many produced (thogh we've got an estimate of "at least as many as tracking stations", which would be 24 IIRC, and then of course where are they now.