My grandfather, Pieter Schoonheim, gave me the plate 50 years ago. It commemorated his company, "ROTTERDAMSCHE KOLENCENTRAL" which he established in 1931. I believe he had plates made to give to his family although I don't know of anyone else who has one.
Hoping to get more history on the plate which I have no doubt is real Delft pottery. It's traveled with me all these years and hung in a place of honor in all my homes.