UNIT pass

While acting as UNIT's scientific advisor, the Third Doctor had a UNIT pass in the name of "John Smith". When the Thirteenth Doctor's TARDIS had to make an emergency landing in the Third Doctor's UNIT HQ laboratory, Yasmin Khan found the pass and peered at it curiously, without realising it belonged to another incarnation of the Doctor, a fact the Doctor herself didn't remember either due to temporal disturbances messing with her memories. (GAME: Lost in Time)