Is it possibly Caerulea Plena? There are a couple of doubles (blue) more recently available but I don't know how many years back they go, if those could match your purchase. Double Trouble, Macs Double

morz8, I compared mine to Caerulea Plena, Mac's Double and Double Trouble, if anything it's very close to Mac's Double. I bought mine in the late 80's from Sterling Perennials in Ontario, It could be a sport of an introduction of theirs called 'Rondeau Sapphire' which I bought along with Osprey and Zwaneburg Blue. I couldn't find 'Rondeau Sapphire' anywhere on the web to compare the color but just now found an old catalog of theirs (much ransacking) the description for R.S. is light sky blue and as I said the first few years it had single flowers. I now think mine is a sport of Rondeau Sapphire. I think the mystery is solved, thanks for your help it got me headed in the right direction.

Annette