It was basically a man's pleasure to look at these drawings

Dorothee Schmid Christie's

"It's an amazing collection," said Christies specialist Dorothee Schmid. "Usually people have one or maybe two, but to have such a wonderful collection of that variety of drawings is amazing."

It is thought that they were put in a folder in an attic by the original buyer which other family members later found but did nothing with.

"It is only now that they have decided to sell them and it is really spectacular because is it very rare that you have drawings by this artist which are signed by him," Ms Schmid said.

The drawings have been well preserved

Klimt only signed works he sold - and he sold very few sketches before his death in 1918, meaning those left were stamped.

It is not known whether the original Austrian buyer was a friend of the artist - but it is likely that he went to Klimt's studio and picked out the 17 sketches, mostly of women.

"It was basically a man's pleasure to look at these drawings," Ms Schmid says. "It was not necessarily something that was brought to decorate the living room.

"So that's also why they're still in good condition because 100 years ago it would have been totally inappropriate to put something like that up on a wall."

'Fresh and beautiful'

Colours from red and blue crayons have been preserved especially well because the pictures have not been on show, she said.

"They're still very fresh and beautiful so it is for us an amazing find."

They will form part of the auction house's German and Austrian Art sale, which also includes works by Max Beckmann, Emil Nolde and Ernst Ludwig Kirchner, in London on Thursday, 11 October.

The Klimt collection is estimated to fetch between �775,000 and �1,075,000.