Antique pin back bronze medal from the Eighth Annual Convention of the National Association of Post Office Clerks held in Baltimore, Maryland on September 6, 1897.
One side depicts a Pony Express rider while the other is the State Seal of Maryland.
Nothing like it found on eBay, Google Lens, or Google.
Made by J.K. Dawson in Philadelphia (very small mark). Measures 2.75 inches long by 1.5 inches wide.