From Wiki

Moonstick Co. Lunawheel

• Type: circular custom
• Size: 5 Inches / 13 cm
• Material: Plastic
• Scales:
  • Front: century / year and month / day

Instructions on reverse. A three-disk circular slide rule to report moon phase and tide information from AD 1 through AD 4000. It's easier to use than the Moonstick, but doesn't give as much information. It's also based on a simpler, less accurate astronomical theory (although it's more than adequate for anything you'd use it for).

The disk here is set to February 1732 (new style). A glance at the "22" in the inner ring tells us that George Washington was born under a waning crescent. Julian calendar ("old style") settings are available through the 20th century. Manufactured circa 2003.

Moondisks are available from the inventor at http://www.moonstick.com/.