This is a faithful replica of the nocturnal and tide predictor made by Elizabethan instrument maker Humfrey Cole circa 1570 that resides today in London's British Museum. It was used to determine the time at night, and designed for use with Kochab B--a star of Ursa Minor (i.e. The Little Dipper)--because of its high declination in the night sky. To determine the time, a user aligns Polaris (the current Pole Star) with the central hole in the dial. The alidade is then pointed to Kochab which indicates the hour (based upon the current month and day of the year). It can be used thus for another 12,000 years until Vega becomes the Pole Star. The reverse side of the instrument is a tide predictor which was used to determine the time of high tide from the age of the moon (how many days have passed since the last new moon). Brass-plated zinc/aluminum alloy construction. Includes wooden stand. 4" Diam. x 1/2" W. (12 oz.)