For a limited time, the Royal Mint has decided to launch a limited number of Britannia coins with the effigy of Queen Elizabeth II. The minting and production of this version of the 2023 Britannia were terminated by the end of 2022. I suspect that production may be less than 2 million coins.
From mid-November 2022 onwards, the Royal Mint swapped over to the effigy of King Charles III for the remainder of 2022-2023 minting season.
In short, there is a 2023 Britannia with the Queen’s effigy, and another with that of King Charles III, which is now in stock and selling.