A Chinese museum had to be closed down recently, as many of the 40000 exhibits were found to be fake. (source).
According to the news story:
The museum's public humiliation began earlier this month when Ma Boyong, a Chinese writer, noticed a series of inexplicable discrepancies during a visit and posted his findings online.
Among the most striking errors were artifacts engraved with writing purportedly showing that they dated back more than 4,000 years to the times of China's Yellow Emperor. However, according to a report in the Shanghai Daily the writing appeared in simplified Chinese characters, which only came into widespread use in the 20th century.The collection also contained a "Tang Dynasty" five-colour porcelain vase despite the fact that this technique was only invented hundreds of years later, during the Ming Dynasty.
Apparently, China is in the midst of a museum boom and there is a demand for artifacts. This naturally created incentives for fake objects with no or dubious antique value to be brought in for display.
Perhaps the Chinese have been churning out such fake stuff or imitations for centuries. So, if a fake object that was produced in 1200 AD were to be found today, won't it qualify as a genuine fake, with its own antique value?