The Clock Thing

I've only just noticed that almost all clocks that display Roman Numerals use IIII instead of IV to represent 4 o'clock:

Very odd. At first I thought it was the just the one in the van-hire office I was in at the weekend, but then I saw one in an Indian restaurant this evening. It was really starting to bug me. And when I got home, I discovered that my own mantelpiece clock features the very same phenomenon. So I've been surrounded by clocks displaying this incorrect Roman numeral all my life and never noticed...

So obviously, I googled it. I'm not, it seems, the only person to have noticed this and wondered why. There doesn't appear to be a definitive answer, however. Some of the less mundane suggestions are:

The letters 'IV' were an abbreviated for of JUPITER in Roman times, so the Roman used to put IIII on their sundials because they didn't want the face to read 'one, two, three, GOD, five...'.

It's an aesthetic thing - the VIII is quite a 'heavy' character while the IV is not, so the IV was changed to IIII to even up the clock face.

King Louis the something or other was a dumb-arse (well, he was french) and when presented with a clock bearing the IV, he announced that it was wrong and insisted that it be changed.

So there you go.

Have a nice day.