My wife kept quite good records of her peonies. Only three cultivars were planted in this particular garden, allegedly: Myrtle Gentry, Sarah Bernhardt, and Mrs. A. M. Brand. The latter is the one in question, purchased in 2005 from New Peony Farm.
Various other gardens contain Chestine Gowdy, Duchesse de Nemours, Festiva Maxima, Friendship, Glowing Candles, Koenigen Wilhelmina, Mrs. Bryce Fontaine, Old-Time Peony (Pink), Old-Time Peony (Red), Queen of Sheba, and Raspberry Sundae, all purchased from commercial sources, and all match the descriptions here. This "Mrs. A.M. Brand" is the only one giving me trouble. :-(
Very best regards,
Mark