America had been branding and cropping the ears of convicted criminals since colonial times and the punishment was still being administered in several U.S. states well into the 19th century. The abolitionist Jonathan Walker was one notable victim, after authorities in Florida ordered that his hand be branded with the letters SS (for 'slave stealer') for helping seven runaway slaves find freedom in 1844.
It was commonly used in the U.S. for the crime of horse theft. In 1780, a law was enacted in Pennsylvania stating that any individual who ‘feloniously’ took a horse or mare would ‘for the first offense...stand in the pillory for one hour, and ...publicly whipped on his, or her or their bare backs with thirty-nine lashes, well laid on, and at the same time shall have his, her or their ears cut off and nailed to the pillory, and for the second offense shall be whipped and pilloried in like manner and be branded on the forehead in a plain and visible manner with the letters H.T.,’ for ‘horse thief’. The same punishment was being handed out to horse thiefs in North Carolina by 1786, and in Tennessee by 1790, with a slight variation in the letter H being branded on the left cheek and T on the right cheek, as opposed to the forehead.
It is not known exactly when pillory punishment came to an end in the United States, but it certainly continued in some parts of the country into the 1840s or later.
F stands for 'felon'.