Philately is one of the most popular hobbies around the world. Here are some truly bizarre finds that would be a great addition to any stamp collection.

• In 2004, Austria issued stamps bearing the image of a crystal swan—and the image is coated in actual crystals. They were made of paper and then a few real Swarovski crystals were applied with a special, extra-tough glue that can endure mail sorting machines.

• Two years earlier, stamp printers in Gibraltar pioneered the art of putting rocks in stamps. In 2002, the country decided to put actual bits of its famous Rock of Gibraltar into postage stamps bearing the landmark’s image. Limestone was bored from the Rock, powdered, and then mixed in with the ink on the stamp.

• Brazil began issuing stamps in 2001 that promoted its most famous commodity: coffee. The stamps feature pictures of coffee beans and plants, and they’re also embedded with the smell of coffee. (The aromas stay strong for as long as five years.)

• Malaysia has offered a series of stamps depicting some of the exotic animals native to the country, such as the flying fox and the moon rat. Those animals are nocturnal, so to hammer that point home, the eyes on the stamps of those animals glow in the dark.

• Bhutan issued stamps in 1973 that were actually tiny, functional records. Played on a turntable, they included recordings of Bhutanese folk songs and stories about the nation’s history.

• When you think of Switzerland, do you think of wooden shoes? Think of wooden stamps. In 2004, the nation turned some 120-year-old fir trees into a limited edition of postage stamps made from very, very thin wood.

• Switzerland is also famous for Swiss chocolate. Recently he country sold stamps wrapped in foil that when opened resembled a bar of chocolate squares. They look and smell just like chocolate (but when they’re licked they still taste like glue).