A Chinese Kwantung reverse pattern copper dollar is valued at $200,000-250,000.
The 1889 piece is to lead Heritage Auctions' June 22-24 World Coins Signature Auction in Hong Kong.
It was struck in China on machinery ordered from the UK.
As a pattern coin (the second produced for this issue) it differs from the finished coin - in this case the English and Chinese characters around the edge appear in the opposite position.
Heritage explains: "After the design was finalized and the legends moved, it would become the first dragon dollar to be struck on modernized equipment in China, and thus became the standard for all the provincial dragon dollars that would follow.
"As such, this coin's importance in shaping modern Chinese coinage cannot be understated.
"In addition to the historical importance that accompanies this coin, it also happens to benefit from exceptional preservation and eye-appeal."
A 1979 People's Republic of China piedfort set of two is expected to make $110,000-120,000.
The coins (a 35 yuan and a 450 yuan) were struck as presentation issues to commemorate the Year of the Child.
Of the two, the 450 yuan is far rarer, with a mintage of just 500. The 35 yuan was issued in a run of 2,000.
Piedfort coins are thicker than average and are produced exclusively as presentation issues. This was originally so they would be easily distinguishable from regular currency.
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