Hi Mauro,
That's what I thought and as many collector's have thought up interesting names I came up with the 1972-and-a-half variation
The pistol has a 1972 Ulm proof and has number 10.004187.
It seems that rather than production changing from one version to another, they just utilized parts on hand, substituting new parts only when old parts were used up.
I'vel added a frame shot without grip for comparison also.
I also noticed the rather crappy workmanship of the grip screws while removing the grips.