I changed it back to the way I posted it on 14 June 07, before it was erroneously changed on 3 Dec 14. Yes, the letter existed, but it was not commonly found in most printer's type face blocks, so as a matter of practicality, as 'J' was not commonly used in print, the custom was then (now having become tradition) to not use 'J' in either printed/typed or written form to designate a military unit.   