As many of you know, the Pentax Screw Mount Lenses are superb lenses that cost relatively little. Some of the M42 Takumars are considered absolute "classics" and "gems" like the 50mm 1.4 SMC Takumar. Many call it one of the best 50mm's ever made ( up against the likes of Leica's Summicron ). Don't believe it ? Try one out. You'll find stunning build quality (feel the perfect silky smooth focusing ring) along with high contrast and low flare. For pure value, these lenses cant be beat.
PentaxTakumar lenses come in 3 flavors during the Screw Mount period of 1962-1975 ( most optical layouts were the same throughout the period ):
For the most part, double coated lenses 1962-70
About 1971, seven layers of coatings were used
SMC Takumar lenses
Last version of these lenses - rubber focusing ring 1972-75