Here is a Guinness Stout Thermometer from the Arthur Guinness Son & Company located in Long Island City, NY.  This Guinness Stout Thermometer is from the 1940s era and is in excellent condition considering how old it it.

It is approximately 9″ wide and was made by the Cooper Company located in Pequabuck, CT.  Signs like these would often be displayed outside of taverns or distributors to both advertise Guinness Stout and read the outside temperature.