Solving the mystery of clock-face Roman numerals

I was about to buy the clock kit for the Art Deco Desk Clock in issue 208 (Nov. 2011), when I noticed that the Roman numeral 4 is written out as "IIII." I've always seen 4 as "IV" in Roman numerals. Was this a misprint?
—Jerry Nelson, Baltimore, Md.

Although you probably learned "IV" as the Roman numeral 4 in elementary school, Jerry, clock faces often show "IIII" instead. Without a definitive reason, we offer V theories for the discrepancy:

I: One tradition says the IIII form was used to avoid invoking the wrath of the Roman god Jupiter, whose Latin name, IVPPITER, begins with IV.

II: Clockmakers may have held over the form from before subtractive notation was the norm. (However, the IX on the clock face renders this theory inconsistent at best).

III: Another theory suggests that the IIII provided an economical way to cast metal numerals: The four Vs, 20 Is, and four Xs required for a clock face could be cast four times in the form "VIIIIIX." Then each casting could be strategically separated and rotated to form all the necessary numbers. (One VIIIIIX separates into VI, III, and IX. Another into VII, I, and IIX, and so on.)

IV: It may be simply a convenient way to divide the dial at a glance. (Only I shows up in the first third, V begins all the numbers in the second third, and X only appears in the final third of the dial.)

V: Finally, it may be nothing more than a way to balance the clock face aesthetically. Each number mirrors one of similar "weight," creating a visual symmetry, as shown.