The best forgeries... are never discovered to be forgeries.
The faster it is discovered, the worse of a forgery it is.
The worse of a forgery it is, the faster it is discovered.
Several decades = Good forgery.
Ten minutes = Very bad forgery.
The Kenyan BC is in the three minute range.
But then it was a hoax rather than a forgery, so that distinction does exist.
“discovered” by those who planted it, in the first place?
Not very impressive.