Guarding the door is a blue and white porcelain vase almost two meters high decorated with writhing dragons. Behind the glass door a miscellany of things jostle for attention: a broadly smiling pottery boy, an intricately carved bamboo brush holder, a beautifully realized coral figurine mounted on a wooden stand, and shelf after shelf of jade and porcelain wares, followed by a retinue of snuff bottles. All swarm this 100 square meter space, which seems barely half its size because of how cramped it is. On the upper edge of the door hangs a plaque that reads: Ton Ying.

"Zhang's Ton Ying Company does not exist now, but I want to continue the memory, even in a small way," says Chen, who attributes a sizable part of all the antiques in his store now on East 55th Street to the old company. "They were passed to me through my uncle, who bought in a lot during the company's final years and who passed away in 1980 in San Francisco."

Over the years Chen has done his own fair share of research, carefully collecting every piece of information he could find on the old Ton Ying Company, an effort that has resulted in a thick portfolio of newspaper cuttings, printed archival materials and the company's auction catalogs, with the final prices next to each specific item. They are mostly two or three-digit numbers.

"In 1964 a one-room apartment near Columbia University cost me $50 a month," Chen says. "And a porcelain vase made by a master craftsman at the royal kiln of Jingdezhen in Jiangxi province routinely fetched between $50 and $200. Today you cannot expect to save a few months' rent and buy something with a hundreds-of-thousands-dollar asking price at the auction."

In September 2014 a monumental imperial Qing Dynasty vase was sold at auction for $24.7 million at the Boston-based auction house Skinner, topping all sales of Qing Dynasty vases in the US to that point. The anonymous buyer was believed to be from the Chinese mainland.

"There were mainly three factors that contributed to the phenomenal sale," Chen says. "First is its size, measuring 34.5 inches (87.6 cm). Second is its overall decoration that employed a wide range of techniques, which in turn gives it the nickname Ci Mu Ping, or 'Mother of all ceramics'.

"Last but not least is that this vase is almost identical to one housed by Beijing's Palace Museum, and is one of only two of its kind."

In an interview with Antiques and the Arts Weekly, Judith Dowling, the Harvard-trained expert who presided over the record-breaking sale, said the vase "was last seen publicly in 1964 at Parke-Bernet Galleries in New York, where it was in a sale of Asian things belonging to Ton Ying & Company".

"They encountered me at preview and asked to photocopy that auction catalog of 1964, which includes a detailed description and a full-page black-and-white picture of the vase."

On the fringe of the yellow page, beside the description, a number had been written down: 750.

"That amount is a clear indicator that people understood its value even back then. But no one had quite anticipated the rise," Chen says.

"Since the mid-1990s the market for Chinese antiques has shifted gradually from the US and Europe to China, as the Chinese are rediscovering their own cultural heritage."