LONDON (REUTERS) - "Oh, it is unquestionably the great rediscovery in the art world of the 21st century so far. There's not been anything like it." said a senior specialist of Old Master Paintings.

Leonardo da Vinci's Salvator Mundi, a painting of Jesus Christ, is on display at Christie's auction house in London before its sale next month.

It's such a great discovery not just because it was sold for only $60 in 1958 and is now worth an estimated $100 million but the painting has actually been missing for most of its existence.

Dating from around 1500 and having hung in the galleries of English kings Charles I and II, the painting was resdiscovered in 2005.

It was almost unrecognisable when experts found it though.

"He had a heavy beard and moustache painted on, he almost looked like he was wearing a mask and you simply could not see the quality until the process of restoration and the cleaning of these old layers of over-paint were removed." said a senior specialist of Old Master Paintings.

Its rediscovery was followed by six years of intense expert research to document its authenticity.

Christie's has now put the painting on a tour across three continents ahead of its sale.

At the San Francisco display, thousands of people queued for hours to see the work.

The painting will be sold at Christie's in New York on November 15.