This lens is from the Tamron Adaptall-2 line of lenses and can therefore be adapted to almost every SLR system ever made. This lens shown here has the Pentax P/U adapter for the universal M42 screw mount.
The lens is quite similar to the Sigma 80-200 mm lens, but the Tamron lens offers a much smaller minimum focusing distance of 0.90 m which enables a maximum magnification of 1:2.8 at the long end (210 mm).
The lens has a one-touch zoom/focus control system for easy and quick operation. I haven´t yet tested it for its optical quality.