There are more than three.
See the related question below.
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the roman numerals L,X,M,C,I,D ARE the roman numerals that can be used only 3 times
For rules relating to the use of Roman numerals see related links.
Under today's rules they represent 692 in Roman numerals.
As Roman numerals they are invalid because they do not conform with the rules governing the Roman numeral system.
Under today's rules the Roman numerals CMXLVII represent 947.