This is the "Automatic Ink Detection” PCB from an Epson inkjet printer. According to the service manual, it either detects or cleans clogged nozzles (this is not clearly explained). The service manual does say that high voltages at a few microamps are present on this board. The board is connected to the main control board through a flat flexible cable and to a wire grid on top of the waste ink pad/nozzle cleaner assembly through a silicone insulated high voltage wire. The smaller board attached to it with the Matsushita logo and the transformer seems to be some kind of self-contained flyback converter but I could not find a datasheet.
In terms of design, I’m primarily wondering about the irregularly patterned via stitching all over the board and the loops in the PCB traces areas marked L1 and L2. Since nothing on the board seems high-current, the via stitching is probably not for heat dissipation. If anyone knows what exactly the “Automatic Ink Detection” feature does, that would be helpful too.