I just loaded a roll of Kodak Ektar 120 into my 1939 Voigtländer Bessa 6x9. I started winding, looking for the 1 to appear in the ruby window. I wound and wound, but the 1 never appeared, neither did the 2! I was certain that I had wound far enough, but no numbers! I must have done something wrong with the loading or the turning of that little winder thing. It seems simple and I've done it many times before, but hey I wouldn't put it past myself to screw it up somehow. So I went into the dark bathroom and wound the film back onto the supply spool and tried again. Guess what. The same thing happened. I know it is the definition of insanity to keep doing the same thing and expect different results, so I didn't try it a third time. I went where every puzzled photographer goes... the Googlez! It seems that some others have had their Ektar 6x9 numbers go missing as well. Kodak must have recently changed the position of these numbers, because I know that I have shot this film in this very camera in the last few years and not had this problem. Anyway, I pulled out an empty Ektar backing paper and compared the position of the numbers to the position of the window and sure enough, they don't line up. The numbers are too close to the edge of the paper.
Now that I had the problem clearly identified I needed a solution. Moving the window to accommodate the numbers wasn't really an option, so I had to move the numbers. One option for moving the numbers was to just spool the film onto a different backing paper that has numbers in the right place, like Acros. I decided that was sub-optimal since I might get confused later and develop it in the wrong chemicals. So I took that old Ektar paper and wrote on a new set of numbers in the correct position. Then I rolled the film onto the new paper. Voilà!! There are my numbers in the ruby window!
I hope someone finds this useful. I know I did. :P