This is something I never noticed until I chanced upon an online article discussing this issue. Upon reading this, my eyes were immediately set upon the dial of my Longines. Indeed, ‘IIII’ is used instead of ‘IV’. I continued reading the article and found it to be intriguing. The link to the article I read can be found in the references. However, it is a rather long read (9-min read). So, I shall distil it to give you the essential takeaways. The most notable exception to the observation would be Big Ben of London. The Big Ben uses ‘IV’.
I) The first possible explanation for this is that ‘IIII’ was the earliest way to write ‘4’ in Roman numerals. Even though the most common way to represent ‘4’ in Roman numerals today is ‘IV’, it was not always the case. Perhaps watchmakers wanted to continue this tradition. The earliest timepiece models even used ‘VIIII’ instead of ‘IX’. However, this situation was problematic as the numerals ‘III’ and ‘VIII’ were confused for ‘IIII’ and ‘VIIII’. Interestingly, as I write this paragraph, the spellcheck function detects ‘IIII’ and ‘VIIII’ as spelling errors and thus flags them with a red squiggly line beneath them. This does not occur with ‘III’ and ‘VIII’. According to the article, the first mechanical clocks were created in Europe during the 13th century, and Roman numerals were still used extensively then. Most clocks were mounted on churches, and Latin was the official language of the Roman Catholic Church. It thus made sense to use Roman numerals instead of Arabic numerals on the dials of timepieces.
The article then goes on to mention a few other possible reasons that ‘IIII’ is used in lieu of ‘IV’. Here are some possible reasons:
II) ‘IV’ was avoided because it was deemed as an offence to Jupiter, a god in Roman mythology. Consider the word ‘Jupiter’. The letter ‘j’ was one of the last letters to be added to the Latin alphabet. For much of history, the letter ‘j’ did not exist. The letter ‘i’ was used where we would use the letter ‘j’ today. Consider the letter ‘y’ and some names such as ‘Johanna’. ‘Johanna’ would traditionally be pronounced with a ‘y’ sound at the start. Moreover, consider the sound of ‘y’ in words such as ‘gypsy’, ‘rhythm’, ‘fly’, and ‘by’. Also consider the letter ‘u’ in ‘Jupiter’. It was basically interchangeable with the letter ‘v’ in medieval times. In fact, the King James Bible, as originally published in 1611, is a classic example of this. The word ‘love’ would often be spelt ‘loue’, etc. Hence, coming back to what we were originally discussing, we see then that ‘Jupiter’ would have been written as IVPITER. What do you observe about the first two letters of the name?
This issue of not writing down the name of a god reminds me of a similar practice of adherents of Judaism. According to the Wikipedia article on the Tetragrammaton, the written tetragrammaton must be treated with special sanctity. Writing the tetragrammaton unnecessarily is prohibited, so as to avoid it treated disrespectfully. To guard the sanctity of God’s name, a letter within the tetragrammaton is substituted for another letter. Alternatively, a letter is substituted for a hyphen. This practice is applied to the English name ‘God’, which adherents of Judaism would write as ‘G-d’.
III) It was easier for the non-educated folk. The additive notation in ‘IIII’ would certainly have been easier for the majority of the illiterate and non-educated European population. The subtractive notation might have been confusing. When this is coupled with the fact that ‘IV’ and ‘IX’ can be confused for ‘VI’ and ‘XI’, it is easier to empathise with the people back then.
IIII) The ‘Lazy Clockmaker’ hypothesis. This is a hypothesis that is not taken seriously.
V) The Sun King, Louis XIV. One explanation is that like Jupiter, Louis XIV did not want to have part of his name on the dial. However, this theory is quite implausible because the practice of having ‘IIII’ instead of ‘IV’ on timepieces had been around a long time before the birth of Louis XIV.
VI) The visual balance. This reason is one of the most convincing. Consider watches which have ‘IIII’ and ‘IX’ to represent ‘4’ and ‘9’ respectively. The Roman numerals on the watch would be as follows: I, II, III, IIII, V, VI, VII, VIII, IX, X, XI, XII. The first third of the dial would have the ‘I’ type. The second third of the dial would have the ‘V’ type. The last third of the dial would have the ‘X’ type. When the dial has three distinct areas, it is perceived as more elegant and harmonious.
Conclusion: There is no definitive explanation for having ‘IIII’ instead of ‘IV’ in watches. It is likely to be a combination of some of the above reasons. I end the article with yet another exception to the trend:
21 January 2019
P.S. Did you notice that I used ‘IIII’ in the list numbering?