Numerals are completely superfluous anyway. As long as the top of the dial is marked, there is no need for any numbers at all, a series of dots will do. Langlands & Bell have produced timepieces using the 3 letter codes for airports - 'Frozen Sky'
I just read the reason why this occurs while searching for facts for my "Did you know" thread.
Look at the number four on a clock face that uses Roman numerals. If the clock is made correctly then the Roman numeral four is wrong. The standard and correct way to write the Roman numeral four is "IV," but the traditional way to show it on a clock face is "IIII." Legend has it that a clock was made for a British king. When he saw the clock he mis- informedly corrected the clock maker who re-did the clock face to show a "IIII" instead of an "IV" thus not risking offending the king. Other clock makers followed suit so as not to embarass the king. Now it is the traditional way to make clocks.