I'm not an expert on tree peonies and unfortunately I don't recognize that one. It is really gorgeous, though. Don't know if anyone else has come over from the peony forum but we have several people who grow lots of them. There are thousands of registered tree peonies, makes it really hard to figure out names. If yours had a herbaceous peony with it that typically indicates that it was a grafted tree peony though--they're typically grafted onto herbaceous roots. If the herbaceous root is planted at a typical 2" below the ground the herbaceous root can start growing again instead of just providing energy to jump start the tree peony. That will often cause the tree peony to fail, yours looks perfect, though!
Good luck with finding a name for your peony!