This is the preset aperture, earlier version. Takes a little getting used to but like all Asahi lenses of this era very well put together with very smooth aperture and focus. Easy depth of field control with presetting max aperture on front ring then selecting shooting aperture on the inner ring up to the max aperture selected. . Recommended at the cheaper end of this lens family.  Optically and cosmetically A. You can buy this lens for your M42 screw mount Pentax or choose the option of adding a K&F precision M42-E adapter which enables this lens to be mounted on Sony E-mount, focus peaking cameras. Both lens caps supplied.