The year was 1969, almost the peak of the Vietnam War.
A young medical volunteer with a charity hospital in Da Nang had the opportunity to work with residents of the mountains, providing them with basic medical care.
"I was just amazed. The people were just living such a different way of life," says Mark Rapoport, whose interest in Vietnamese tribes was piqued then, and has stayed strong since.
The New York native now spends eleven months every year in Hanoi, looking after his 54 Traditions Gallery located at 30 Hang Bun Street, considered the only one in the country that focuses on the cultures of all the 54 ethnic groups of Vietnam.
Back in the 1990s, when Mark first returned to Hanoi, "there was literally only one store that sold minority things" in the capital.
In 2001, he and his wife decided to make the capital home as he was working on a research grant to study Agent Orange and birth defects in Vietnam and she was getting a position with a US-based NGO in Hanoi.
Mark remembers that at the time in Hanoi, there were about eight or nine stores specializing in selling artifacts from ethnic minority groups.
As the country started receiving more tourists, there were people from the tribal groups and those living in the northern mountains going out to find things they feel would interest foreigners and expatriate collectors.
Mark became a collector and ended up with 15,000 objects between 2001 and 2005.
"I like things that people use. A plough, a rice cutter, things that usual museum collectors would not pay much attention to. I like the tools of everyday life."
Today, the gallery boasts a collection of about 30,000 objects, divided into five themed rooms like "Functional Objects" or "Shamanism."
Its customers include former US President Clinton, the Metropolitan Museum of Art in New York and universities such as Harvard, Brown and Yale. The New York Times has describes it as "more like an ethnographic museum, library, and gallery all rolled into one."
For visitors to the gallery, Mark is more than willing to be a guide through the walls and floors that are adorned with countless objects hand-picked by the owner. Each has a price sticker and a small note describing the object and its origin.
In the old days when he first started collecting objects from Vietnamese ethnic minorities, Mark said he would sit and listen to others, learning every detail possible about the history and cultural aspect of each object.
These days he often spends time at night writing up descriptions of each piece after it has being obtained by the gallery - with the help of his business partner who's an experienced curator, and local expert on ethnic minority culture.
"We give people interesting things and we tell them as much as we know," Mark says. "Anything you buy from us, even for 10 dollars, which for a gallery is a very small number, comes with a write-up."
The collection has considerable variety - a rice cutter from the Tay minority people in the northern mountains of Vietnam, made of wood with a bamboo handle, carved in the shape of a snail; shipwrecked ceramic boxes founded near the Cham Island in central Vietnam dating back to the 15th century painted with lotus flowers, peach blossoms and other flora; and so on.
There are also a great deal of tribal textile products including baby carriers, scarves, blankets, skirts or wedding scarves, in addition to Vietnamese urban antiques, Buddhist statues and ceramic items.
Dorothy Hagen, a customer from Oregon, US, who visited Mark's shop earlier this week, said she loves tribal art because each piece has an individual print that's very unique to the person who made it.
"Today a lot of people are going back to the handmade kind of things because they just have more value," she said. "It's not like the mass-produced stuff."
These days the gallery also hosts lectures on topics in tribal art, organizes customized field trips to villages and offers consultations on identification and authenticity. Recently many objects were auctioned to generate funds for Operation Smile, the program that provides free surgeries to children with facial deformities.
Asked when he would stop working at the gallery, Mark says, "As long as I stay healthy. We love being in Vietnam. There are 54 groups and subgroups so there are a lot of different things that interest us."