Real Masonic Initiate Apron!
These were originally used by us for the limited edition packaging of The Occult Technology of Power, but there are a few unused ones. There are slight variations from one to another, and I've produced a photo that shows three variants so you get an idea of what yours may look like. They are all clean though may be a little wrinkled.
All white, cotton, and are stamped "Friendship Lodge #160 / Portland, Oregon" on the back.