This collection of metal airplane signs is produced on American made steel and made in America. These porcelain enamel signs use a process developed in the early 1900s that produce the vivid colors seen on each aviation art sign. Powdered crystals are applied and then baked onto the steel plate to provide a long lasting and durable finish. Rivets are then drilled into the metal to make the sign easy to hang. These novelty aviation signs are now true collectibles as they are no longer produced in the USA nor on steel. All are limited to stock on hand.