Agree absolutely.
My F67 is NEF, an accidental find in a cheap tin of stuff.
My F77 is NVF, and my F78 is NEF, both cheap, not noticed, on Ebay.
I've yet to see any advances on those three on Ebay, and I've been looking for 10 years....
I think I remember Michael Gouby told me a few years ago that DNW had asked him to go through a collection of pennies to help them identify the varieties but, as they didn't offer him anything for his trouble, he declined.