Give us more details. How big is the bloom? Is it scented and if so, how much and what does it smell like? Do you have other peonies or what else is blooming at the same time (is it early, mid, late or bloom week)? Single bud or does each stem have side buds? How tall/wide is the shrub? It's very pretty but there are several very full dark pink peonies out there, is there anything completely distinct about this one? It's pretty full, if it's a large bloom does it stand up well to rain/wind? If so you might be able to narrow down the choices that way, might be designated as a landscape peony for the strong stem.
Was just on Hollingsworth Peonies facebook page and noticed a pic from 3 May that could be a contender for your peony, name is Mmm Emile Debatane. Take a look at it, can probably find it on their website if you don't do facebook, see if the description fits. Here's the facebook address, too, just scroll down for the older photos.
https://www.facebook.com/holli...