Since 1824 courtesy of Leo Reynolds on Flickr

Notice the first letter of the inscription. I and J were used interchangeably by scribes to express the sound of both the vowel and the consonant. It wasn’t until 1524 when Gian Giorgio Trissino, Italian Renaissance grammarian known as the father of the letter J, made a clear distinction between the two sounds. Once he distinguished the soft J sound, as in “jam” (probably a loan sound), the current phoneme for J was born. Source: dictionary.com
The letters missing from the Greek alphabet are Q and J.
We see the Latin inscription, INRI, on the cross, instead. In the inscription above, all the words are run together. Find INRI by picking out the first letter of each word: I for Iesus, N for Nazarenus, R for Rex, and I for Iudaeorum. No J's in there, and the confusing v is u. U dig?