I found this interesting;

"Although there is some debate as to its origin, It most likely comes from the primary cause of the Six Day war, which was the closing of the Straights of Tiran. For certain however the designation Ti-67 is a Janes or other printing house fantasy or a miscopy that became its nickname."

"Acccording to IDF designations there are three Tirans, Tiran4, 5, and 6. Four for theT-54, five for the T-55 and Six for the T-62. While there have numerous updates and modifications of the Tirans I have been unable to find any sub designations for them. or rather any IDF designationtions media ones abound."

http://idf-armor.blogspot.com/2008/12/peace-for-gallile-1982-lebanon-war.html