Cheng Po-hung in his 100-sq-ft shop full of rare stamps, postcards, pictures, coins and banknotes. Photos by Nicole Wong

All the crumbling buildings and cobbled streets scattered throughout Hong Kong have a story behind them.

And if anyone can narrate those tales - as well as point out their historical and intrinsic value - it's probably going to be Cheng Po-hung.

As the honorary advisor of the Hong Kong Museum of History, Cheng, 60, is a Mr-Know-It-All when it comes to Hong Kong.

But for him, that love of history is more than just a consulting gig or reason to wax poetic about the past.

In a small, 100-sq-ft shop called Commonwealth Co in Central's Shing Lee Shopping Arcade, Cheng proudly collects history and shows it off.

Sitting against the backdrop of rare stamps, postcards, pictures, coins and banknotes, Cheng offers an engaging insight into the disappearance of "old Hong Kong" and his lifelong passion as a collector of its history.

A photocopy of a 1924 local newspaper archived at the University of Hong Kong.

Like many children with an interest in collecting, Cheng enjoyed cutting the stamps off of letters his parents received, and then trading the small prizes with classmates. But unlike most of his classmates, Cheng's passion never burned out. As an adult working at a brokerage firm he started at in the late 1960s, Cheng expanded his collection to include coins and banknotes. A fitting transition, considering he dealt with currency on a daily basis.

"I came across many rarities when some clients brought in foreign banknotes to exchange for local money, or when they wanted to cash in silver coins," Cheng recalled. "I couldn't help but buy the coins or banknotes from the firm's owner before they were melt into silver bars."

And Cheng did not stop there. Rather than simply admiring his collectibles, he set out to learn about their history. He quickly became a regular at local libraries and joined both local and overseas numismatic associations in the 1970s.

Cheng's inclination to preserve also led him to old pictures and postcards of Hong Kong he acquired the late 1980s. Browsing through photos in galleries and books, Cheng often noted ambiguities in the dates or the locations of the pictures taken. The desire for discovery again saw Cheng deep in research.

"I want to know the history behind everything," he said. "Seven years ago, I bought a rare picture of the Hong Kong Mint - on Sugar Street in Causeway Bay - which was opened in 1886 and closed in 1888. There're few records of the building, though it marked a historic moment in Hong Kong."

Cheng's assiduous research soon established him as a renowned expert on Hong Kong history and attracted the attention of local publishers. Since 2001, Cheng has written 15 books on a wide range of topics that shed light on the city's history in the last two centuries.

In his book on early Hong Kong brothels, the opening of the city was closely related to the blossoming of western prostitutes around Lyndhurst Terrace in Central in the mid-19th century. When the government wanted to develop the Kowloon Peninsula, Chinese prostitutes began to flock along Temple Street in Yau Ma Tei.

There is a story behind the current Chinese name of Lyndhurst Terrace, which means "flowers along the street", Cheng pointed out. In the mid-19th century, the "pimps" nicknamed their working girls "high quality honey" in newspaper ads and stated that clients would have to bring flowers for the "honey" when they visited.

"It got so popular that florists sprung up along Lyndhurst Terrace, then spread to Wellington Street and Wyndham Street past Lan Kwai Fong. The government adopted its popular Cantonese name as the official one in the 1920s," Cheng elaborated. "The few florists around Lan Kwai Fong today are in fact remants of this history."

Over the years, Cheng has invested at least HK$1 million in his more than 10,000 pictures and postcards, not including the money he spent on his countless esoteric stamps, coins and banknotes.

Much of Cheng's knowledge of local streets, however, was accumulated as he left his footsteps all over the city.

Princess Theatre in Tsim Sha Tsui in 1958. It closed in 1973 and the Miramar Hotel was built at the site.

"During the global financial crisis from 1973 to 1974, I sat for the exam for a taxi driver's license in case I lost my finance job," Cheng recalled. "It was essential to be familiar with all the streets on Hong Kong Island and Kowloon in order to pass the test, so I spent three months exploring them."

That exploration led to more research, as Cheng sought out the origins of the streets' names. Elgin Street in Central, for example, was named after James Bruce, the 8th Earl of Elgin, England's high commissioner to China who ordered the deconstruction of Yuanming Yuan in 1860.

With the city's infrastructure and history imprinted on his mind, Cheng passes his knowledge onto Hong Kong youth through his many talks, seminars, workshops and general studies courses he has offered at local universities since 2001. The youths, Cheng said, show a great interest in local history.

"Once I went on a three-hour field trip with 40 students, from Central to Wan Chai. It was raining hard and many of us were soaked," Cheng said. "We stopped under the footbridge on Canal Road and I asked them if they had any further questions. They stood there and talked for a whole hour."

The older generations also visit Cheng when nostalgia comes flooding back. Many Hongkongers who were born in the 1950s, Cheng noted, are in search of pictures and postcards of the city from their childhood and teens, since very few people had cameras at the time.

"Many of these customers are now well-off past their 50's and are willing to pay a premium for their memories," Cheng said. "Hong Kong changes so quickly that any given scene on the streets can disappear in a few years, which is why these photographic records may become more valuable than you can imagine."

Besides his commitments at the universities and publishers, Cheng also writes regularly for the Hong Kong Monetary Authority's quarterly newsletters and local exhibitions.

Despite being 60, Cheng still delights in his work as a collector, historian and owner of his shop - a meeting place for those who share similar interests.

"My shop was opened in 1992 with my wife as the shopkeeper for five years. I quit my finance job in 1997 to take up my current work full time. I haven't looked back since," Cheng explained. "I'm my own boss and nobody can force me to retire. I can go on to do what I love for as long as I like."

There are plenty of voyages into the past for Cheng to look forward to. A highly sought after commentator on local history, Cheng's schedule is filled with interviews in the local media and various organizations.

But his family, he admits, has long since lost interest in his historical work and media exposure.

"I've always supported my family and paid for my sons' and my daughter's education, so they let me be," Cheng said with a laugh. "They used to tape my TV appearances in the early days. Now they think of me as an old man who babbles too much in public."

(HK Edition 02/01/2008 page4)