Pentax's fast vintage telephoto — the Takumar 135mm f/2.5 in M42 mount.
The Asahi Takumar 135mm f/2.5 is an early M42 screw-mount telephoto lens produced by Asahi Optical before the Super-Takumar designation was introduced. The Asahi Takumar designation indicates single-layer anti-reflection coating or uncoated optics, predating the Super-Multi Coated (SMC) Super-Takumar generation.
135mm focal length, f/2.5 maximum aperture (fast for a 135mm of this era), M42 screw mount, single-coated or early coating formula.
The Asahi Takumar 135mm f/2.5 is notable for its fast f/2.5 aperture, uncommon at this focal length and making it useful for available-light telephoto and portrait work. Single-coated optics provide less flare resistance than later multi-coated designs but the characteristic rendering appeals to many film and adapted digital shooters. An earlier and rarer variant of the Takumar telephoto line.
Inspect all elements for haze, fungus, and cleaning marks — single-coated lenses are more susceptible to coating degradation. Confirm M42 thread engagement is clean. Aperture blades should be oil-free. Check for any damage to the focus or aperture ring.