London, England (CNN) -- She reputedly never carries any bank notes, but Britain's Queen Elizabeth II this week marked half a century since she became the first ever monarch to be depicted on one.

Sketched by artist Robert Austin, the young queen first appeared in a £1 note in 1960 wearing a crown, earrings and a necklace, her likeness replacing images of Britannia -- a female symbol of Britain used on the country's currency for centuries.

While her firm gaze and faint smile remain unchanged, the image of the queen has aged visibly over the decades, albeit very gracefully.

A new image appeared in 1963, the year she marked her 37th birthday, and again in 1970 and 1971, the last of which survived unchanged for nearly two decades. The current image in circulation, showing an older queen, again wearing crown, necklace and earrings, dates from 1990.

With the queen still officially head of state in many Commonwealth countries, Elizabeth II also features on many bank notes worldwide -- making her image one of the most widely reproduced of all time.

To mark the anniversary, the Bank of England's museum this week opens an exhibition of past and present banknotes featuring the queen in addition to the original pencil sketches and printing blocks used to create them.