My best guess: Sign has been amended over time and several vinyl orders. At some points, the original font spec was lost or the vendor changed, and they did a best guess match, which most people can't do accurately. Also people don't anticipate the need to keep precise records of old specifications.
Some process problems are also evident in the manual placement of letters and counters (LaoGai) leading to jittered letterspacing and baselines. Not to mention the variation in size, horizontal and vertical scalings. Not sure if any letters have been applied upside-down but this does happen…