Flashaholics have been hoping for a AA version of the E01 for years. The closest I've found is an Arc P with a AA body, or, even better, I have a Peak Kilimanjaro SS with a single led.
I have this, which is an E01 head in a cheap $2 AA body. Not tough though, dropped a few times and the head is only pressed in so it pops out all the time.
It may be easy to tell which iteration is which by the packaging. When they updated the lumen output for the 2nd iteration, it was still advertised as having that 21 hour runtime IIRC.
Hmm, I still have the box from August 2013 and that does mention the 21 hour run time but does not mention output anywhere, but this was the one modded my Vinh. Not sure what generation it is. The very first one I got came in a blister pack. I think you are on to something there.