That's the one I always used.  It was this first time I saw it when I was 13, when I saw this one girl's typing on a "test" she gave me.  I hadn't seen that capital "I" for a 1 in over 35 years, until I watched the movie "Finding Forrester," where he had a filing system in which he used the same letter "I" for a 1.  I guess more people use that than I had previously thought.  Ockham's Razor, eh?  Simplest answer is usually the correct answer.