just a lil heads up, if.. you iron it, try a corner first cause if its has been printed using thermal process, then the heat of a iron can blacken or blanken the plans.
its not a widely spread print method as far as i know, but i heard of it being used before, to make plans degrade over time, so people cant sell em on that easy, or have to buy new set if they wait to long with using it. kind of a exparation date method.