They were turned out in large numbers specifically for the purpose of advertising.  One of the ways to identify a pre-pro glass is by the thinness of the glass wall and base compared with modern shot glasses - they were clearly not intended to withstand the rigors of bar use.  The low glass content meant that costs were kept low and hence they could be obtained for as little a 35 cents per dozen. 

The allure of this cheap and easy way of marketing was embraced fully by distillers, blenders and rectifiers, liquor stores, and even bars and hotels. Thus, a shot glass enthusiast is faced with a dizzying number of variations to collect.  Although it's very difficult to estimate exactly how many different kinds of pre-pro shot glass were produced, it's probably in the range of ten to twenty thousand. 

The distillers lead the way in terms of production volume.  The most common pre-pro glasses surviving today include those produced by the Hayner Company of Dayton, OH,  Sunny Brook Distillers of Louisville, KY, Detrick Distillers of Dayton, OH, and the Security Distilling Co. of Chicago, IL.  Whereas the 'Fulton Whiskey' ad on the previous page was probably aimed at the saloon owner, it's easy to find similar enticement ads aimed at individual consumers.  The 'Security Rye Whiskey' ad that appears next to the Jell-o girl on the first page is taken from the advertising pages of The National Magazine, 1904.  It tempts consumers with the promise of a free shot glass with every bottle ordered.  The fact that these Security Distilling Co. shot glasses are one of the most common found today stands testament to the success of the company in persuading customers to buy!