Its worth 800 pounds, I'll sell it for you for a commission of 25%
I will do so by adding it so some massive list of poorly advertised plates on my website, its massively unlikely anyone will ever buy it, but that doesnt bother me as ive nothing to lose, and if it does sell im quids in.


Thats roughly what an "expert" valuation will be.

Plates are worth what someone will pay for them, end of, and unless you find such a person, then its worth nothing.