In the end Donald Pleasance is credited as JEN instead of SEN (in the film they say SEN so they made a typo). Not a lot of care was put into this film.
Anyway, from this description (sorry, in Italian) http://www.cosedaunaltromondo.it/product.php?pId=1403&printp=1 I see that whoever reviewed it watched the very same version I have because it refers to "germs of thought" and that gender differences have been abolished because they lead to unhappiness (same stuff that the added voices in the background say)
After some researches I also found that:
1) the Italian poster http://www.cosedaunaltromondo.it/english/tipologies_dettail.php?tId=80 was designed by Averardo Ciriello. PRINTER was GRAFOPRESS, 1976, ROME. DISTRIBUTOR:
SOCIETA' ITALIANA DISTRIBUZIONE FILMS, 1976, ITALY
2) "Società Italiana Distribuzione Films" is also the distributor written at the end of the movie I have
1+2= this version that I have was the first available (1976) and distribuited. So I can safely assume now that this is the standard pre-DVD Italian version.
Why is this film rare then? Because the version available on peer2peer and torrent websites have been "made" using the English video and adding the Italian audio. Someone must have had some troubles re-cutting all the pieces because of the missing scenes, the extended scene and the prologue were lost in the process.
After 2004 you can only find the DVD version (which is a new dub, horribly done but accurate to the "original cut") so this is really getting rare to find... and the last chance to preserve SEN extende scene