One pack contained 8 cards. PR05 was enclosed in Megami Magazine, probably June 2006 edition. It was one of 3 cards randomly distributed in that edition of the magazine (at a guess, the others were probably PR04 and PR06).
Three of the promotion cards are box cards.
This set used to be called just “Broccoli High Grade Collection,” but there are actually a few different High Grade sets for Nanoha. Confirmed that this one is the Nanoha & Nanoha A's.