Essential for meterology, medicine, industry and scientific research, thermometers are not the result of a single invention but an evolution spanning about 2000 years. 

The Design:

Featuring an antiqued finish, the coin is inset with an operational dial thermometer. Including both Celsius and Fahrenheit scales. The thermometer's face portrays an Aztec-style sun in the middle, surrounded by Aztec-style patterns and iconography based on the circular Aztec agricultural, or solar, calendar. 

The coin's obverse reveals the thermometer's sensor which is encircled by Aztec-style patterning, the Ian Rank-Broadley effigy of Her Majesty Queen Elizabeth II, monetary denomination and 2018 year-date.