In Oceania we call this CUD, although I believe in US its called something else I've sold many NZ dollars with similar 'cuds'. This one might be called 'Queen with wart on nose' In the UK they ask ridiculous amounts for these - 100's of pounds.
US calls them cuds as well, but usually when they are attached to the rim. Otherwise it's just a die chip if it's not connected to the rim. They are super common on American coins, but I don't know the values on British coins
Extreme example on ebay asking £600 https://www.ebay.co.uk/itm/165662500095?hash=item26924124ff:g:CQQAAOSwOQdjF3NX
Just adding the reverse for any one interested Crowned Tudor rose dividing date and legend, denomination below.