This is a hidden limit lense , Pentax SMC FA50mm f1.4. It have standard focal-length and good focus-ranges. It can be used in both of Film SLR and DSLR.
Name brand "POLAR" is a korean company known as "Samyang Optics.". They products Samsung SHD and D-Xenon(for DSLR) lenses (OEM).
My Polar 35-70mm f3.5-4.5 lense was produced since 1985. (not exactly assurance) There is no A connecting point. but it works well on Pentax P3 photo sensors.