Plates pressed into ends of railroad ties

While sitting at Trackside Pizza on the Springfield line I noticed at the track outside that the ties had white plate or screen on their ends . Whats the purpose of this ?

In short, its to keep the tie ends from splitting apart.

Ok . For years they never had them . Do you know when this started ?

When Technology improved, the Nail plates are about same as used on factory made rafter beams.
A galvanized plate stamped to have 300 or so nail like protrusions that are pressed into end of tie.

Prior to this age ties many times had a "S", brace pounded into the ends.

yeah, what TB said. the "S" irons were/are there, you just dont notice them, because they are flush inside the tie ends, and they are untreated metal, and rust quickly, looking like the end of the tie. the stamped tin plates are probably cheaper, is why you see them now.