You have a very interesting early one-piece button, dating around the 1780-1820 period. The "Tallio" fox hunting design and wording is seen occasionally on sleeve links of the period (two oval one-piece brass pieces similar to small buttons, and connected by brass links). The round examples of the "Tallio" design, in regular button style, are rarely seen.
Gold "TALLIO" cuff links were discovered in an archaeological dig in the root cellar of George Washington's Boyhood home, Ferry Farm, across the Rappahannock River from Fredericksburg, VA. The fox is running in the opposite direction, but otherwise looks the same as your find. Take a look at image number three of the following article in Fredericksburg.com: