The 1813 holey dollar which sold in Melbourne for $410,000 in August 2012.

The 1813 holey dollar which sold in Melbourne for $410,000 in August 2012. Photo: Jason South

Police are hunting for a thief who stole $1 million worth of rare coins -  including one that sold for $410,000 two years ago - during a brazen robbery at the State Library of NSW.

Dr Alex Byrne, the State Librarian and the library's chief executive, said the thief broke into a coin case about 3.40pm on Wednesday and escaped with 12 coins, including examples of Australia's earliest currency that Dr Byrne said were "historically, extraordinarily important".

The theft was captured on the Sydney library's CCTV system and footage has been handed to police. They have launched an investigation into the incident and believe it may be linked to a second theft from a hotel later on Wednesday.

The dump, cut from the centre of the "holey dollar", was worth 15 pence when it was in circulation.

The dump, cut from the centre of the "holey dollar", was worth 15 pence when it was in circulation.

Dr Byrne said 15 coins, part of the library's collection, were on exhibition in a "secure locked case" in a gallery at the library.

"Late on Wednesday, somebody came in and, after hanging around for about an hour, broke into the case. It was really very difficult to break into. Eventually he, I presume it was a he, did get in and made off with 12 of the 15 coins on show," Dr Byrne said.

He said the thief used some sort of tool or implement to break into the case before stealing the coins, the most notable of which was a "holey dollar", an example of one of the first coins struck in Australia.

A "holey dollar" sold in Melbourne in August 2012 for $410,000.

Dr Byrne said that at the start of the 19th century, Governor Lachlan Macquarie recognised that there was no coinage in Australia so he bought 40,000 Spanish dollars. The dollars were large coins, and Governor Macquarie had a hole punched through the middle.

 The central plug, known as a dump, was valued at 15 pence, and the outer ring was worth five shillings. The coins were re-stamped and went into circulation in 1814.

"Historically the holey dollar is extraordinarily important. It's about this country developing all the aspects of a civilised society," Dr Byrne said.

"This theft is very disappointing and upsetting for all of the staff here."

Dr Byrne said there were other holey dollars in collections in Australia, but he was unaware how many and said they were very valuable.

He said the library was open to the public at the time of the theft. The library is understood to be reviewing security in the wake of the theft.

Police said that a second theft took place about 5.20pm on Wednesday, when a man entered a hotel on George Street and approached a glass cabinet. The man removed four sets of diamond earrings, three diamond rings and a gold pendant from the display.

These items are believed to be valued about $75,000.

Police are investigating possible links between the two crimes.