Congrats for getting it Séamuis,
seems to be a good investment as well as an interesting lens to use. Here's some more from the trusty
Frank Mechelhoff a.k.a. Taunusreiter:
Press text: One of the world's brightest retrofocus wide angle lenses for single lens reflex cameras. Edge-to-edge sharp resolution at full aperture; unique lens design without distortion; suitable for architectural photography.
Remarks: This was the first "Auto Takumar" non-standard lens, as well as the first fast SLR wideangle "reporter lens" (marketed Autumn 1958) which gave Pentax a clear advantage. It was replaced in 1963 by a Super-Takumar 2.0/35 with even bigger filter! (67mm) and more weight. It's one of the nicest lenses of the early period, well made and not heavyweight.
Performance wise it shows significant chromatic aberrations at high aperture (probably because of the great distance of the single front element to the correcting group).
Nonetheless an important lens for every Early Pentax collector...

This pic also from the
same excellent source