Petri 55mm f1.8 - That old brand you might not know about - Lens review

At the end of 2019 I was at this event where they sell a bunch of old cameras and lenses and obviously I bought a few, but among the various items on display for the first time I saw many lenses and cameras branded Petri. Initially I thought it was some obscure Italian brand but, as one of the vendors explained to me, it's actually Japanese. I did a little bit of research and turns out it was established in 1907, so it's pretty damn old, but eventually went bankrupt in the 80s and the brand was acquired by Cosina, which is slightly more known in the vintage community So I browsed a little bit the selection of cameras and lenses they had and eventually decided to buy this 55 millimeters f1.8 mostly because I didn't know the brand, it was cheap and this specific one comes with an M42 mount instead of the Petri mount, which I guess no one makes an adapter for. And, yeah, you might be starting to see a pattern here: I have quite the habit of buying l...