The Pentax - M SMC 50mm  is the standard focal length partnering lens with the Pentax K1000. At max aperture F1.7 an excellent choice for light challenged scenes.  An A+ lens and optically perfect.  You can buy this lens for your K-mount Pentax or choose the option of adding a K&F precision PK-E adapter which enables this lens to be mounted on Sony E-mount, focus peaking cameras. Both lens cap.

Pentax-A 50mm F1.7 K mount S#1716875