April 12 will mark the 50^th anniversary of the first man in space and Sotheby's is auctioning a unique piece of memorabilia to commemorate the event.

Three weeks before Soviet Yuri Gagarin orbited the earth, a test capsule, Vostok 3KA-2, was sent up on a trial run.

Carrying a life size dummy, the 2.5m diameter cabin successfully completed a single orbit of the Earth on March 23 1961, before landing in the snow near the Soviet town of Izhvesk.

The achievements of these times are considerable when one considers that the Wright brothers' first powered flight was made just 58 years previously.

Estimates for the Vostok 3KA-2 capsule range from $2m to $10m

Experts and potential investors are divided on the worth of the capsule, which is currently on display in New York ahead of the sale, with Sotheby's pre-sale estimate spanning $2m to $10m.

"Not only are there no other examples outside of Russia of the world's first spacecraft, this capsule was pivotal in space history as providing the green light for Gagarin's spectacular achievement," said David Redden, the head of Sotheby's special projects department.

"It's an extraordinary object that makes [the history of the flight] real and also totally terrifying."

The anonymous consignor bought the capsule from Russia in a private sale.

The Vostok 1 that Gagarin took into orbit resides at the museum of rocket manufacturer Rkk Energia.