The world's first postage stamp Penny Black went on display at Sotheby's Hong Kong Gallery on Tuesday.

The Penny Black, a pristine impression and unused, was issued in 1840 and was the first known postage stamp in history, according to Sotheby's Hong Kong.

The issue of the stamp is believed to lead to the birth of prepaid postage system.

The design of the stamp was simple, with a small and now iconic portrait of the young Queen Victoria's head in profile with the words "postage" and "one penny." It was an adhesive stamp with gum on the back which was revolutionary at the time.

The Penny Black is set to be auctioned off at Sotheby's in London of Britain on Dec. 7 with a price estimate of 4-6 million pounds.

The exhibition in Hong Kong, which runs until Oct. 30, also included ancient Western and contemporary art works. (1 U.S. dollar = 0.72 pounds)