...all of the ones I have seen have been on post 75 vehicles (I think 75 is the cutoff date) so technically not legal.
There was a topic about this in 2015:
Silver/black plates cause confusion!.
The cutoff used to be 1973, which is when the requirement for reflective plates was introduced for new cars, but since the "Historic" class was introduced black & silver plates have been legal on cars that are over 40 years old.
If you do a Google search you will get conflicting information and references to the 1975 date. I think the main cause of confusion is this DVLA page:
What’s the story with black and silver number plates?, which mentions 1975, but that is a blog entry written in November 2015 and hasn't been changed since.
The DVLA's publication
INF04 contains the updated detail. The latest version says:
Since April 2018 vehicles manufactured before 1 January 1978 can display the older style plates.
You must:
• have applied to DVLA
• be registered within the ‘historic vehicles’ tax class.
Vehicles constructed 40 or more years ago are exempt
from tax. The 40 year exemption date rolls forward
automatically each year on 1 April. So if your Morgan is tax and MOT exempt you can also legally fit it with old style plates.
