I'm pretty convinced this peony is Sarah Bernhardt. Looking at many photos online has showed me similar colours and the faint red border on some petals. Same height and leaf colour too!
I think part of my confusion is because the same nursery that I bought this from had some large flowering plants for sale that were labeled Sarah Bernhardt but those plants had medium pink flowers.
This was over two weeks ago, so the timing was a little early for what should be a relatively late bloomer. I think now in hindsight that those "Sarah B" tagged blooming plants were likely a different cultivar.
I don't have very many peonies currently but they are almost all done. We have had an early season here. Just this last plant and one bloom off Marie Lemoine.
Thanks once again, Liz.