Numeral on some sundials Crossword Clue

 The answer to the crossword clue "Numeral on some sundials" is IIII.

This is an unusual numeral that is sometimes used on sundials instead of the more common IV. The reason for this is that the IV numeral can be confused with the VI numeral when the sundial is not in direct sunlight. The IIII numeral is less likely to be confused with other numerals.

The IIII numeral is also sometimes used on clocks and watches, but it is less common than the IV numeral.

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