Roman Numeral 9 (and 4)

It is usually assumed that the correct way of expressing number 9 in Roman numerals is IX. This assumption is generally correct, but very often you will see number 9 shown as VIIII. Although this looks quite strange and almost wrong to the modern eye, this was a completely valid way of writing 9 in Roman times. My theory is that using VIIII instead of IX creates a sense of a natural progression of numbers. If you decide to use this old convention for your own numbering purposes, make sure that instead of IV you use IIII for 4, otherwise the resulting numbers may look inconsistent.