Thorens strobe

My Thorens TD-124 has a strobe light that works but there are no markers in the strobe window to set the correct speed. Do these little dashes in the strobe wear out? How do I get this repaired?
A little research has led me to believe that a platter with the strobe pattern for the 124 was made available later. There used to be cardboard discs with the strobe pattern printed on them for checking the speed. There may be a place on the web that has a way to allow you to print one of these out...