Dr. M. M. Fenner produced a product called Dr. Fenner's Kidney and Backache Cure. The product was sold widely, and the bottles in which the product was sold, while collector's items today, are common enough that they are not very expensive.
Dr. Fenner was a commuity leader in Fredonia, such that in 2010, despite his death more than 100 years ago, the Fredonia Fire Department has a unit called the "M. M. Fenner Hose Company."
The cure was sold in units that required the use of two values of the battleship proprietary series. Dr. Fenner's only made use of the 5/8c and 2 1/2c stamps. On these two values were used two types of cancels. Type 1 is characterized most prominently by diagonal or slanting outer vertical strokes on the Ms in the cancel. Type 2 is characterized by vertical strokes on the Ms. These types are known to appear within the same sheet of stamps and there is an example below.