Maxwell, I've been a Maggie owner for many years, my next door neighbor and audio buddy owned SMGa's for several as well. As I recall the SMGa's used planar/magnetic drivers for it's entire operating frequency range; I believe it was a two way design. This was before Magnepan's introduction of it's quasi ribbon design; although a true ribbon was used in the top of the line systems at the time (MGIIIA's and Tynpany's).
I loved the SMGa's. Typical Maggie sound: GREAT sounstaging in a smaller than my MGIIIAs' package, not super resolving but very natural sounding and surprising (if well placed in the right room)bass; for the size. I always envied their size (my MGIIA's are so darn big), and thought they were attractive looking. My friend drove them with an Audiolab integrated with good results for the most part, although they sounded underpowered to me. They really came alive with my greater tube watts. Maggies love tubes!
Is this a good deal? Probably, but be wary of one thing: even if they look mint, the worst potential problem may be out of sight. Older Maggies, my beloved MGIIIA's and another friend's included, are known to suffer from corroded wiring on the mylar diaphragms; this will cause failure of that driver. If the speakers were always used with their socks on in a dry environment, you're probably ok. If it's possible to lift part of the socks off you can check for whitish spots on the wiring that crisscrosses the mylar. This is a sign of corrosion.
Good luck and let us know how you make out.