this one use to be a tree peony, and it was broken off @ the base of the plant by constructions workers, i guess this is the flower from the root stock that it was grafted on.
another peony flower
I have the same flower, from a similar situation.
Funny and sad at the same time. I lost a really nice tree peony, but this year the plant was almost twice as big it ever was before and covered in blossoms extremely similar to yours.
must have been a commonly use root stock.