This 50mm distributed by Sears, but is the same lens as the Ricoh P Rikenon 50mm F2. The Aperture of this lens ranges from F2.0 to F16. It has a 6-blade diaphragm and a 5mm filter since. My particular lens is in excellent condition, has a Pentax mount (easily adaptable to the NX1 with suitable lens adapter) and is stamped with S/N: 309399.
I will post some links to other online reviews and photos, but in general this is a sharp vintage lens at greater than f5.6 with good color saturation. Minimum focus distance is about 2ft.
The mount is metal with a plastic barrel; however the lens feels solid and focus adjustments are smooth. This lens can be found online for around $15-$25 depending on condition. For that price the lens if totally worth it.
All photos below were taken hand-held on a bright-sunny day. No 'post' effects except that the 28MP photos were re-sized to 1920x1080.
Yellow flower is a Mariposa Lilly photographed in southern Arizona near the Mexican border.
Read more at on the AUTO SEARS 50mm f2 here: