What about Time Spiral timeshifted (purple) cards, Masters Editions cards and cards from Preconstructed decks?
Commons from Masters Editions and Preconstructed decks are legal in formats where those sets are legal. Essentially, this means Classic and format based on the Classic card pool (Prismatic, etc…) Timeshifted (Purple rarity symbol-TSB) cards are rares for PDC purposes (since that is their equivalent rarity, from a frequency point of view) and so are not legal. Note, again, that proxies are allowed, so, for example, a TSB Disenchant cannot be played in a Standard PDC deck, since since Disenchant is not a common in a Standard set, but it can used as a proxy in PDC Classic, since Disenchant is a common in Classic sets (Seventh Edition, Ice Age and Mirage).
