Just led here by a nice new photo. I found the cultivar description page slightly odd: "Hints of China blood were noted in 1933."

Given that all modern HT's rely on genes from R. chinensis cultivars, like 'Old Blush' and the other famous ones, it would be more surprising if there were no hints of "China blood" in DMSR. Offhand I'm not sure what the 1933 reference is referring to (obviously Kordes knew all about the ancestors of modern HT's).