[thecatspajamas]

How big is that photo, and what is on the front?

FWIW, it just looks like a pretty generic numerical stamp to me. Could be a date (assuming it coincides with the event on the front), or could just as easily be some sort of in-house file coding. From what I've seen, TSN was very inconsisten about dating their photos, with many either having no date on the back or else a hand-penned date which may or may not have been done at the time the photo was received.