Credit Certificate taxed as a Promissory Note

Hammar Bros. White Lead Company sent this $2.50 credit certificate to a potential customer in order to induce a new order. Although it was never used, because it promised a potential credit it was taxed as a promissory note. The tax for promissory notes was 2-cents per $100 or fraction thereof. It's an unusual example of the application of the tax on promissory notes. Can anyone offer other examples of credit certificates like this one?

Hammar Bros. White Lead Co. $2.50 Credit Memo
St. Louis, Missouri June 3, 1901

Detail of stamp and cancel
Hammar Bros. White Lead Co.
Jun
3
1901

Requirements for using the certicate were detailed on the reverse side.

Reverse Side of Certifcate

The accompanying letter further explains the offer and, as was customary of the time, showed the company's plant as part of the masthead. Somewhat curiously the letter is dated May 22, 1901, almost two weeks earlier than the certificate, and the amount of the certificate, $2.50, was added by a penned notation.

Hammar Bros. Promotional Letter 5/22/1901

Masthead detail showing the company's plant in East St.Louis

Note the references to the B. & O. R.R.; the L. & N. R.R.; the Vandalia Line; and the E. St.Louis & Carondelet Line. Click on the masthead image to enlarge it.