You can buy most of these from Chinatowns all over the world. I got some myself a few years ago. I don't believe they are authentic, but maybe cheap copies of the original. Original / older / more authentic coins would be more darker in color due to the passage of time.

If they are authentic, they might sell for a high price: The Manchus ruled China for 267 years: From March of 1644 when the Manchus invaded Beijing and lead to the last Ming emperor to commit suicide after killing off all his family members and chopping off one of his daughters' arms, who in one account became a nun somewhere in China, up to the coup d'etat in October of 1911 when the Sun Yat-sen and the Nationalist party revolted and ended the last dynasty in China.

Emperor Ch'ien Lung / Qianlong ruled China from 1736 to 1795? [about 60 years: He dare not rule longer than his grandfather Emperor Kangxi / Kang Hsi, who ruled from 1662 to 1723 : about 60 years on Gregorian calendar, but based on the Chinese calendar, it's 61 years!].

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