I would not pass up a good deal on L100's but it would just be to compare them to my L100T3's for a few days...
4312A has the 035Ti tweeter, along with 4412.
4312 has the cone type tweet, see here:
http://www.lansingheritage.org/html/jbl/specs/pro-speakers/1983-4312.htm
I much prefer the 4411 with the 044 dome tweet or the 4412A with the 052Ti dome tweet and improved mid, 104H-2. Those are sweet! Mostly it's the mirror imaging that does it for me though, even with my eyes closed and the grilles on, I still hear the lack of it when comparing my 4412A's to my L166's.