If I am not mistaken, it's proprietary, but still made by Dedacciai. If you look on the Pinarello webpage, they list the Prince as using "Pinarello SL" tubing. It's still made by Deda, but exclusively for Pinarello. The Opera is listed on Pinarello's site as using "Opera Pegaso Pinarello", but it is really just proprietary shaped Deda EOM 16.5 steel. Pinarello uses exclusive sizes and shapes that Deda doesn't sell to other frame builders.
If you look on cbike's website (one of the US' s bigger Pinarello importers), they list the Galileo as using Deda 7003 Alloy tubing. Pinarello doesn't put tubing stickers on their frames anymore, but it is still all Deda tubing.
Russ