I was looking at license plates on cars today. Somehow it randomly occurred to me that it would be cool to encode a message upside down in a license plate.
The plate would read like an ordinary jumble of letters and digits. Until, that is, you turned it upside down, and then a secret message would appear.
There are only certain letters and digits that this works for. I think I now have the complete list.
In the chart below, the first line is the character you would use, and the second line is how that character would read when the message is flipped upside down.
The matches aren’t all perfect, but then they don’t need to be. The message just needs to be readable:
A b d H I M N n O P q S u V W X Z 3
V q p H I W N u O d b S n A M X Z E