The thermometer sign in itself is not a rare piece. My research shows it to be a favorite advertising format for many products, for the first half or more of the 20th century. Dr. Pepper signs of many versions can be found with thermometers. Many using the “Enjoy Hot or Cold” slogan. This particular version, inclusive of “the friendly Pepper Upper” text seemed to be a bit more rare in nature. The sign was painted on as opposed to porcelain which may have affected durability and decreased production rates.
Basecamp Vintage & Archives 