The image shows a Great Britain 1897 Charity Poster Stamp, also known as a Cinderella stamp, issued for the Prince of Wales's Hospital Fund.
Here's more information about it:
These stamps were essentially advertising "stamps" or gummed stickers used to promote and raise funds for the Prince of Wales's Hospital Fund, which was established in 1897.
The stamp depicts a mother with children, symbolizing the charitable nature of the fund, and includes the text "1837 The Queen's Commemoration 1897" and "Prince of Wales's Hospital Fund".
This particular stamp has a face value of "2/6", representing two shillings and sixpence, which would have been the price at which it was sold to raise money for the charity.
The Prince of Wales's Hospital Fund later evolved into the King Edward's Hospital Fund in 1902 and is now known as the King's Fund, a significant charity supporting healthcare in the UK.