Rationing coupons collected by a citizen in Zhengzhou. [Photo by Sha Lang/Asianewsphoto]

Most of his rationing coupons were from the circle he got acquainted with on his business trips before the "cultural revolution" (1966-76) ended.

"From what I know, the covert underground market of collection was active, despite the tightly controlled planned economy. Some discerning people knew the value of antiques and they foresaw that the ending of a political era means the inevitable destroying of old things," recalls Li.

He collected ancient coins at first until one of his educated uncles in the countryside suggested that he focused on rationing coupons, because "too many people collect old coins and the coupons have special meanings to the times".

He married a illiterate yet clever villager Wang Laosi, who is 15 years younger than him, in the early 1980s. Wang has been helping him run the grocery store till now.

"I did not understand his hobby at first and thought it was a waste of time and money," Wang says. "I know his collection is worth a lot of money today. But I don't think he will sell them."

When asked how much money he had spent on his hobby over the years, Li held up three fingers and lowered his voice: "Three million yuan ($500,000). This is the amount my wife knows. But in actual fact, I spent much more than that."

He has about 200 old friends in his circle across the country. They rely on the postal system, helping each other exchange and buy the coupons.