During the 1790s and early 1800s, England was under threat first from the French revolutionists and then Napoleon as he took over more territory in Europe. The coins and tokens from the era are quite interesting. A subset of that group are the emergency counterstamped crown sized coins that the British Government issued which culminated in the 1804 Bank of England Dollars. In the late 1790s there was a severe coin shortage in England. One stopgap solution was to counterstamp the crown sized coins the Bank of England had on hand. Most of these pieces were Spanish 8 reale coins, but French pieces and even a few U.S. Dollars were issued. A U.S. Flowing Hair dollar with the King George III counterstamp The first pieces, which were issued in 1797, had a small oval shaped counterstamp of George III. These pieces were valued at four shillings and nine pence. They were quite unpopular and subject to some witty jabs like “Two king’s heads, but not worth a crown” (5 shillings) and “The head of fool on the neck of an ass.” In an attempt to beef up the security on the counterstamped coins, the bank made the mark larger and more detailed. This King George profile had been used on the 1800 Maundy Penny. Counterstamp and 1800 Maundy Penny Once again U.S. dollars were on rare occasions used as the host coins. Although the larger, more detailed counterstamps relieved the counterfeiting problem, it was still not a satisfactory solution. The Bank of England teamed up with John Bolton to use one of his more powerful, high speed press to produce a completely new coin, the 1804 bank dollar. The coin was valued at five shillings. Although all of them are dated 1804, they were produced on a regular basis until 1811. The Bank skipped the possible steps of melting down the silver and reforming it into planchets. They didn't even bother to remove the design from the host coins. They just struck over them. Therefore these coins are sometimes seen with the undertype of the host coin on them. Such coins can carry a premium price, especially when the original date is still visible. The piece I have posted above does not show any undertype. Later the bank would issued two more pieces, a 1 shilling and 6 pence, and a three shilling piece. These were tokens, not coins.
I have a couple in this category too: There are endless varieties of both these. Over 20 versions of the Bank of England dollar are listed, but beware as both these and the Countermarked coins are much copied!