You probably won't see it listed on your wall calendar or desk journal, but today is an unofficial holiday to honor a mechanical device that dominated the 20th century workplace. It's World Typewriter Day!On June 23, 1868, American inventor Christopher Sholes was granted a patent for his typewriter, the first to be commercially marketed. It looked a bit like a toy piano, and could only type uppercase letters. It was one of the first devices to revolutionize the world of communications. And check your laptop or smartphone - Sholes' QWERTY keyboard layout is still in use today.But manual typewriters aren't just found in museums and attics. Even the digital generation loves collecting and using them. Actor Tom Hanks owns over 50 vintage typewriters and has written a book of short stories about his passion for the devices. Todd Moe spoke with David Wells, an avid Vermont typewriter collector and school principal, who lives near Montpelier. He uses manual typewriters in the classroom, to write essays for his blog about old typewriters, and to admire. Wells has about 30 vintage machines in his collection.