BRUSSELS (Reuters) - When President Barack Obama was sworn in for his second term on January 21, it's a decent bet that one of the flags fluttering behind him on the U.S. Capitol was made in Belgium.

The Waelkens flag company, based in the small town of Oostrozebeke in Flanders, supplies around 2,000 flags a year to the United States, with clients including the Pentagon and other U.S. government departments as well as the United Nations.

But it's not just the far side of the Atlantic where the company is gaining ground - it also makes flags for NATO, national militaries, the European Union and just about every country in the world, from China to Nigeria.

"We have a lot of know-how about how we have to make flags and a big tradition of embroidery," said Benedikt Waelkens, who runs the company with his brother, David. "There aren't a lot of people in the world who can and are making handmade flags."

Benedikt said clients keep coming back because of the company's unique flag-making knowledge and its faithfulness to tradition. National and institutional flags have extremely precise guidelines about how they must be made - down to the number of stitches per centimeter and specific fabric shades.

What began in 1928 as a family business making embroidered garments for priests is now, four generations later, an international enterprise with a growing reputation.

Nearly half of Waelkens' flags are embroidered - some even by hand - setting the company apart from competitors who produce printed flags. David believes embroidery carries more symbolism and likens it to art, since a handmade flag can take four or five days to complete.

Benedikt said a large, handmade U.S. flag costs about 400 euros ($540). Waelkens has four-year contracts with the EU, NATO and the United Nations - each of which have scores of buildings and hundreds of ceremonial rooms that fly flags.

Benedikt explains the business in terms of hierarchy: the highest-profile EU or UN officials have the nicest flags in their offices - made of silk, embroidered and with fringe. But below the top, there are hundreds if not thousands of other civil servants who also have banners, albeit of lesser quality.

During the financial crisis in 2007, Waelkens moved its screen printing business to Romania, but the brothers say they want to keep most of the company in Belgium for tradition's sake.

Benedikt wouldn't give details on the privately held company's income but said 2012 was its best year. He attributes the success in part to consolidation in the industry as well as to the company's vertically integrated model - it makes, sells and markets its flags and even produces the flagpoles.

But perhaps the key to the business is its personal, family touch - some of the brothers' current employees also worked for their father and with their grandfather.

"Human capital of the company is the most important thing," said Benedickt. "Happiness of your people, you cannot buy that."