My Eecloonaar UCI Encyclopedia of Registered Pros has a very small listing for Jan De Reus.
He raced in the Netherlands born in 1909 ( and appeared to be still with us in the late 1990's when the book was published)
They list him as the
An Amateur in 1931 Champion of Pays-Bas ( I don't know what the American name is for that country) He participated in the 1933 Tour of Flanders