Hi Joaquin, I agree. I have always wondered about these smurfs too.
Having just checked (again) all my books and catalogues, the only mention I can find of these smurfs is in the big purple book, Unauthorized Guide to Smurfs Around The World.
They are on page 122 (I don't know if you have this book) and are described as "Novelty Figures". The books state that these were released in 1979 and give a value of $15 - $20 each.
How accurate the information is I really don't know I am afraid. I know a few collectors who have had these for many years and as I mentioned in my previous post, although I had always regarded these smurfs as fakes, but as time has gone bye and I have seen more and more of them I think I will have to think again.