It's a bit on the side, but I remember my father telling me that the PCB's he sold to the Eastern Bloc were often adorned with microscopic greetings in Cyrillic, though the Russian spelling was often pretty bad.

Just like now, the Soviet Union was under heavy sanctions, and they weren't allowed to receive the latest computer tech. The various companies had ways around this, though, and the saying was that they'd purposefully design their boards so that Russian engineers could "tamper" with them in order to achieve higher than allowed clock speeds.

Anyway this cute board just made me think of that, so thought I'd share it.