From what I can tell from the jackiis (labeled as such) that I got from GNYOS show. Although I have to say no flowers yet so, I can not be 100% sure.
However:
-The jackii leaves have smooth surface & thinner (the malipoense leaves have very rough surface, in fact the veins would be prominently raised if the plants are very happy & healthy)
-The underside of jackii has less red pigment (much more sparce) the malipoense has dense pigment.
-The jackii alba leaf underside has no red piment at all.
-the top of both jackii are quite similar, alba has more white background.
Jackii are not often seen sold (in fact I bought mine at the time I still collect phalaenopsis ,I did not even know much about slipper orchids and what paph jackii are, I just felt bad not buying anything at the stand if I talked to the vendors too long) So it was quite a beginner's luck for me in this case.
How did you happen to come across so many to give away? I believe they are quite expensive, you must have very happy friends.
By the way, If you post pictures of you plants close-up with number to them, I think SlipperTalk members can spot which one is malipoense & which one is jackii for you.