I can understand where this confusion has come from
It is totally misleading
Why the DVLA have chosen to link the black and silver plate explaination in the same articles as the 40 year rolling tax exemption explanation is beyond me
It is a completely separate issue
It should say that silver and black plates can be used on vehicles first registered on or before 1975 and unlink it from any mention of this rolling 40 year tax exemption scheme