Commonwealth Mineral Spring Water Is The Best "And Don't You Forget It" Hidden Message

[Boston, Massachusetts]: Commonwealth Mineral Spring Water, 1900. Very good. Minor toning, one or two spots.. Advertising card for Commonwealth Mineral Spring Water, with a humorous image of two men on the recto alongside bold claims for the water's efficacy as a cure-all: "It is a sure cure for Dyspepsia, Liver and Kidney Complaints, and other Chronic Diseases". On the verso is a curious message hidden in code. Measures 5.5" by 2.5