Roman numerals didn't have a set formalized use. Throughout the Roman period you'll find different uses IIII or IV for 4. Subtractives are also common IX and using just the base one for numbers IIIIIII. This carried on into the Elizabethan period. The sun commonly has the extended version XVIIII rather than the subtractive XIX. But IIV would be unusual as it doesn't add up right. But it wouldn't surprise me if it was an error carried over from the original Tarot of Jean Dodal. There are enough numeral errors on public buildings of the time that it is quite likely for something like this to have been done wrong.
