Haven't seen this posted or documented anywhere...
2 printings of 2 #1
A strange coincidence that you just discovered this as there's an eBay auction (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190227536675) for a letter from Ketih Green to Olaf Stoop (dated "24 May, 76") wherein he tells him about his intentions of reprinting 2, along with 2x2 and some others.
That's interesting, well all of those are known now except 2 #2. I'll have to look at my copies, but I think they are all 1st prints (anyone see one with other than a $1 price?).