The Promaster Spectrum 7 100-300mm f/5.6-6.7 MC Tele Macro is a telephoto zoom lens for 35 mm SLR cameras. The one I own has a Pentax K-mount and was mounted to my Samsung NX1 using a Fotasay adapter.
Given a 1.5 crop factor for the NX1's mirrorless system, that makes this lens a 450mm equivalent. Let's see how the lens performs from the photos below.
....and zoomed-in below:
300mm Focal Length f16 / 1/100 sec / 0EV / ISO100