Website/Catalog  (1960)  Page(s) 17.  
 
Tree Peony Hybrids or Lutea Hybrids
Crosses of the Japanese Tree Peony (P. moutan or suffruticosa) onto P. lutea or P. Delavayi. These bloom through the first half of June, sometimes longer. [...]
Because these hybrids fall rather naturally into a few large color groups, I have listed them by color, with the suggestion that when ordering, you either specify a group number only, or allow me some latitude in substituting. [...]
6. The "Mystery" Group. Ivories, pearled shades, suffused mauves. Single to double.
Harlequin  Small flowers, blended mauve and ivory cream.

Article (magazine)  (Jan 1955)  Page(s) 25.  
 
Varieties Raised in America. All by Professor Saunders...
The "Mystery Group." Ivories, pearled shades, suffused mauves, single to double...
'Harlequin,' (1952)

Article (magazine)  (Jan 1955)  Page(s) 57.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Lutea hybrid, Lilac Rose, 'Harlequin' (Saund. 1952), [Gardens] Scott Foundation

Magazine  (Mar 1954)  Page(s) 22.  
 
Hybrid Tree Peonies
...By far the most important work with these hybrids has been done by Prof. A. P. Saunders and his originations now number about 80. Their color range is truly remarkable. [...]
The list of hybrid tree peonies following is up to date as far as we could make it.
Originations of A. P. Saunders, Clinton, N.Y.
Hybrids of suggruticosa, lutea and Delavayi.
Harlequin, Semi-double, mauve to cream. 1952.