Air Canada still have their 'fleet number' on the nwd, as well as on top of the tail.
About 18 months ago, at Heathrow, I saw an El Al 767 being towed to remote parking, and I noticed that on the nwd it had '635' rather than the normal 'last two'. I never did find out exactly why, but the nearest idea that I could come up with was a 'door-swap' with an AC 767.
Most of BAs fleet have the 'last two' on the nwd, execpt for B747-400 G-CIVD which wears the 'last three' on the nwd (so it doesn't have VD on the door) - that's my theory, anyway.
One more 'odd one' that I've seen is the 'Air Jamaica' A.340s which have '350' and '351' on the nwd - no idea why.