Watch List notes:

Britannia Gold £100 One Ounce a Mint Error - Mistrike, undated a uniface piece with the reverse design not struck and with a faint impression of the reversed Queen's head, obverse with radial background, as S.BQ23 (2018 and 2019 issues) Lustrous UNC and of correct weight. A highly unusual piece, gold mis-strikes form a tiny percentage of all mis-struck coins, this being the first we have seen on a Gold Britannia issue

Estimate: 1600-2000 GBP