The coins replaced counterpunched 1797 (Round) and 1804 (Octagonal) marks on Spanish dollars. Legal tender in 1804 - Maurice Bull (English silver coinage 2020: 260). The coins were issued May 20th 1804 and valued at 5/- (60 pence) each. In 1811 they went to 5/6 (66 pence per coin) and on May 1st 1817 devalued back down to 5/-. On March 25th 1820, they were demonitised completely.
The great recoinage was in 1816, but actually coins dated 1816 were only issued in March 1817, also no crowns (5/-) were issued until mid 1818, meaning these dollars lasted 16 years, and 14 years as a crown sized coin.
Three shilling and 1/6 bank tokens were also issued between 1811 and 1816, a ninepence was proposed and proofed, but never issued. 5 and 10 pence tokens were issued for Ireland.

My example, a common and well struck type, in which you can not see any of the Spanish coin underneath it.
Before 1804, Bull explains that the counterpunching was mostly on Spanish 8 reales issued from 1759 to 1803 (Carlos 3 and 4) and a few earlier Pillar dollars of Philip 5 and Ferdinand, but also scarce examples exist of 4 and 2 reale coins as half and quarter dollars, a French 5 francs coin of 1801 and even a US dollar from 1795 was counterpunched, all are basically unique.

The usual type of dollar used (Unused example, Mexico city 1801). The Treasury made a profit buying the dollars at 4/3 or 4/6 each thus making a profit of at least 6d per coin.
I love coins. Especially silver, gold and anything really old.
Member of the Royal Numismatic Society of New Zealand and the Auckland Numismatic Society