I had a similar fun problem with a little tool for use with an ATSC TV tuner.
For context, while NTSC program selections were typically indexed by channel ("ABC here is channel 4, NBC is channel 6"), ATSC uses "subchannels" like "12.1" or "21.5". I had assumed these could be safely stored as a decimal type.
Then one of the broadcasters here introduced both "42.1" and "42.10" and it broke the key model in the underlying SQLite database I kept the channel info in.
