During the 19th century counterstamping of coinage was done as a means of advertising one’s business and also as a forerunner to the modern day shopping coupon.
Dr. George G. Wilkins was the most prolific counterstamper of coins in the United States during the mid-1800s. Estimates range to more than 100,000 coins, mostly large cents and small cents. He seems to have stamped everything crossing his path, though no silver dollars or gold coins are known.
There are two different styles of counterstamps: Large letters with very little space between the “N” and “S” of Wilkins, small letters with full space between the “N” and “S” of Wilkins.
This 1856 Liberty seated dime is one of the specimens not previously known. Examples were 1835 Bust Dimes, 1842, 1853, 1853 with arrows, and 1857. There are seven specimens recorded (known to exist).
This is why I continue to collect coins, medals, and tokens; new doors always open up to me after fifty years of collecting.
Resource: My personal coin collection and “United States Tokens” by Russell Rulau.