Happy Birthday Barbie! A look back at the career and collectability of a US icon

March 9 is the 52^nd birthday of a very special lady - Barbra Millicent Roberts, better known as 'Barbie'.  The evergreen doll has been on sale for over half a century and we thought we'd have a look at her glittering career and collecting highlights.

The fashion doll, produced by American toy giant Mattel, was invented by businesswoman Ruth Handler in 1959.  At the time, children's dolls resembled infants; yet Handler noticed her daughter Barbra - after whom Barbie was named - liked to give her toys adult roles.

Allegedly inspired by the German doll Bild Lilli, Handler decided to create an adult fashion doll that could be sold to children.  The revolutionary idea was highly successful; Barbie made her debut on March 9 1959 at the American International Toy Fair and went on to sell 350,000 units in the first year of production.

Over five decades, it is estimated that over a billion Barbie's have been sold in more than 150 countries, with Mattel claiming that three are sold every second.

The most expensive Barbie on Earth - complete with diamond necklace

In that time, the iconic doll has seen many incarnations: the twist 'n' turn Barbie of the late 1960s, the talking Barbie, Malibu Barbie and the archetypal Superstar Barbie - featuring masses of blonde hair and a big grin.

The inexorable rise of Miss Roberts hasn't been entirely smooth - she has consistently been criticised for promoting an unhealthy and unrealistic body image, something Mattel attempted to rectify with a re-modelled, curvier Barbie. 

In addition, the talking doll got into trouble in the early 1990s for uttering the phrase "Math class is tough!" - construed as stereotypical sexism.  Despite these bumps in the road, Barbie has remained popular - and collectible - for many years.

In 1999, De Beers celebrated Barbie's 40^th by designing a special doll, wearing a gown encrusted with 160 diamonds.   It had a price tag of $85,000.  In 2006, Dutch fashion designer Ietje Raebel sold her collection of 4,000 dolls - dating from 1959 to the 2000s - which had an estimated worth of $185,000.

Included was a mint-condition Barbie #1, in zebra-striped costume - it realised $6,000 alone.  However, this was trumped by an incredibly rare 'Midnight Red' Barbie from 1965, which was sold at Christie's for $17,091, a world record at the time.

But the most expensive Barbie of all sold only last year - beating the previous record by more than 17 times.  The doll wore a Stefano Canturi-designed black dress, as well as pink and white diamonds weighing 4 carats in total, and realised an enormous $302,500.

In Barbra Roberts' case, it goes to show you that age and experience can't be beaten; so, if any toy collectors out there have kept hold of their vintage Barbie dolls - and can bear to part with them - now might be the time to regard them as an investment, with significant profits to be made.