[Leon]

Only recently have some of the thinner series come out in more quantities. I have been watching these for my whole 15 yrs of collecting as an adult. My observation is that the paper thin ones are quite a bit scarcer than the other two varieties. The Factory 4's are in fact the most commonly seen followed by the Factory 11. My thought is that it does in fact have to do with the very thin stock they (Kotton-Never Go Out) are printed on. That's just my (quite studied) observation. Of course others could have observed things differently. I think it took me 3-4 yrs to find my first thin stock one. For my own record I classify them from easiest to more difficult as type 1 (Fact. 4), type 2 (Fact.11) and type 3 (Never Go Out)....best regards