There's 2 different ways of writing Roman numerals. Additive and subtractive. Subtractive was invented later. If you go back far enough, "IIII" is correct, and the ONLY way to write it at the time. Clock faces often use additive numerals--check it out, it's not hard to find a clock or watch that has IIII instead of IV.
And you can also see if the watchmaker has a clue about what they're doing by checking the 9. If they used IIII, they should also use VIIII. But a lot of the time you'll see IIII combined with IX, which is just wrong---that'd be like mixing ancient greek and modern greek.