what is wrong with this watch?

[Thomas Okken]

The Wikipedia article on Roman numerals gives a good overview on just how little standardization there is, or has indeed ever been, when it comes to the use of subtractive notation.

Even today there seem to be disagreements. Specifically, some people seem to believe that subtractive notation should only be used with the next lower power of 10, while others do not consider that to be a requirement. So, for example, in the closing titles of BBC TV shows, they show the year the program was made using Roman numerals, and as the 20th century drew to a close, I observed both MCMXCIX and MIM for 1999.