On the east end of one of the platforms at 30th street station I noticed a box affixed to a roof support that had a series of numbers 1-possibly 9. The numbers are made using round holes cut in metal to form the individual numbers. It appeared to be so designed to be lighted from behind. At no time did I see an lights on in the box. Anyone familiar with this box and what function does it serve? (I do have a photo, but I won't post unless know one is familiar with the item in question.)