Is 4 IV or IIII?

Looking at this image of a clock that I chanced upon in St.Goar in Germany, I was surprised to see why the number 4 was written as "IIII" and not "IV." Reading up a little bit, I found there is no single explanation for this. Rather, there are multiple explanations and several of them might be true. The one that I found interesting was this on Wikipedia:

With IIII, the number of symbols on the clock totals twenty 'I's, four 'V's, and four 'X's, so clock makers need only a single mold with a V, five 'I's, and an X in order to make the correct number of numerals for their clocks: VIIIIIX. This is cast four times for each clock and the twelve required numerals are separated:
o V IIII IX
o VI II IIX
o VII III X
o VIII I IX
The IIX and one of the IX’s are rotated 180° to form XI and XII. The alternative with IV uses seventeen 'I's, five 'V's, and four 'X's, possibly requiring the clock maker to have several different molds.