I found a board by dumpster diving. I am almost sure that it is SMPS board. I didn't understand black strips at the bottom of the PCB marked by red rectangles. By the way, it is a single layer board with all thru hole components. I couldn't peel off them. They most likely on bare PCB like a solder mask layer.
Can anyone explain usage of this strips? My first thought was isolation but i am not sure about it. For example, the rightmost one is wierd. Does it provide an extra isolation layer in addition to the solermask between traces and legs of component?
This is photo of the other side. Sorry about quality. At that moment, I can't take a new one. Bottom-left corner of the following photo corresponds to bottom-right corner of photos above.