Why is number 4 written as IIII and not as conventional IV in watches or clocks with roman numerics?

Answer 1

Sorry, I've never seen that.

Answer 2

The notation of Roman numerals has varied through the centuries. Originally, it was common to use IIII to represent "four", because IV represented the Roman god Jupiter. The subtractive notation (which uses IV instead of IIII) has become universally used only in modern times. For example, Forme of Cury, a manuscript from 1390, uses IX for "nine", but IIII for "four". Another document in the same manuscript, from 1381, uses IV and IX. A third document in the same manuscript uses IIII, IV, and IX. Constructions such as IIIII for "five", IIX for "eight" or VV for "ten" have also been discovered. Subtractive notation arose from regular Latin usage: the number "18" was duodeviginti or “two from twenty”; the number "19" was undeviginti or “one from twenty”. The use of subtractive notation increased the complexity of performing Roman arithmetic, without conveying the benefits of a full positional notation system.
Likewise, on some buildings it is possible to see MDCCCCX, for example, representing 1910 instead of MCMX – notably Admiralty Arch in London. Another notable example is on Harvard Medical School's Library which reads MDCCCCIIII for 1904.
Another likely tale is that the low literacy rate made it difficult for some to do subtraction, where the IIII notation could simply be counted.

Answer 3

I think they do it to differentiate it from VI (6) so people don't get confused, because the 6 is upside down and already kinda looks like IV.

Some of the more modern clocks will use IV.

Hope this helps!