The following might be of use to rosarians attempting to identify found white HTs.

From an advertisement for Cromwell Gardens New Roses
in the American Rose Annual of 1921, p. (ii)

"Mrs. John Cook. Color, ivory-white, occasionally suffused with light pink during cool weather but usually opening clear white in every petal. The bud is firm and of nice formation, opening into a cup-shaped flower of enormous proportions, but without a trace of coarseness in any stage; the large flaky petals are of splendid texture and are well-rounded in form. When well established, it will produce flowers larger than Frau Karl Druschki...The growth is robust in character, branching continually from the base, producing long stemmed flowers of exquisite fragrance, and developing a rugged, hardy plant."

I wonder what was meant by the phrase, 'flaky petals'?