Number plate
From Tardis Wiki, the free Doctor Who reference
The Doctor's TARDIS was capable of tracking number plates. (TV: Resolution)
The number plates of two police motorbikes were 532 PPL and 452 YMF. In the Gatwick car park, several cars' number plates were visible, including 937 DFS, 768 WEF, 378 YXS, a grey car with the 378 YMS number plate, a green car with the 378 YMS number plate, 378 LAF. (TV: The Faceless Ones)