This is a vintage prime. Specifically, a Tamron SP 300mm f/5.6. It's passable for telephoto landscapes, but is seriously lacking in contrast for my taste. Plus, the contrast peaking doesn't work on this lens, instead highlighting areas of chromatic aberration rather than areas in focus. I've resorted to using magnification to focus but it's... awkward at best.
The lens was in a box with a Telemore95 II x2 teleconverter. The teleconverter just turns the image into a soup of softness. I understand, I could turn the lens down to f/11 to make it better, but that's obscenely slow for wintertime overcast weather. I already have to go up to ISO 400 to use the Tamron.
I didn't spend any money on this vintage gear though. It's... inheritance, and it was in a box full of Contax and Yashica gear, combined with an M-Mount camera and a pair of lenses for it. The M-Mount lenses give the best results, but the super-telephoto at a low price of buying an adaptor seemed great.
Now, I just feel like I only want to get the Olympus 300mm. I don't have PDAF though.