The Asahi Pentax Takumar 500mm f/5 is a manual-focus super-telephoto prime built for the M42 screw mount, dating from the early years of Pentax's Takumar line. It was designed for distant subjects such as wildlife, sports, and aviation, and pairs naturally with classic Pentax SLR bodies.

At UK auction the Takumar 500mm f/5 is a thin market: the only verified hammer result on file is £138 from June 2022, which gives a working reference point for what a usable copy sells for at saleroom level today rather than a retail asking price. With a single data point the true value range is uncertain, and condition, completeness of the case and hood, and the presence of clean glass will swing the price either side of that figure.