(FORTUNE Small Business) – As soon as news of the deal broke, outdoorsmen were skeptical. Last January, C.C. Filson, a storied 107-year-old maker of outdoor clothing for hunters and fishermen, was sold to a private-equity firm in Los Angeles called Brentwood Associates. To run Filson, Brentwood named a new CEO: Doug Williams, a former executive at Polo Ralph Lauren. Hunters and guides who swear by Filson's clothes as the toughest outer-wear in the woods feared that Williams would cash in on the brand's authenticity and open, say, mall locations in which to sell Filson bathrobes. It was a little like finding out that John Deere was being taken over by a Cadillac executive.

Williams's résumé was impressive enough. In 1988 he took an entry-level job at Polo, and he ultimately rose to the position of group president, where he oversaw global manufacturing and relaunched the women's clothing line. But one aspect of his background made him a better fit for the Filson job than his skeptics realized: He's a longtime hunter and fisherman. Asked whom he considers the core Filson customer, he replies, "I am. When Brentwood contacted me about the job, they wouldn't come right out and tell me the name of the company. They said, 'We're thinking of acquiring a hunting and fishing company in Seattle.' I said, 'Oh, you mean Filson?' I went home and rummaged through my hunting gear and realized I was already its best customer."

As the new Filson CEO, he now embarks on the delicate balancing act of raising Filson's profile and financials (the company is profitable; in 2004 it took in about $20 million in revenue) while remaining true to its heritage. What happens if he doesn't get the balance right? "Well, there's always Chapter 11," jokes Kurt Barnard, a retail analyst who consults for large clothing brands.

Williams dismisses that kind of pessimism. "I read the complaints in these Internet chatrooms about this yuppie from New York who will turn Filson into another Eddie Bauer or Abercrombie & Fitch," he says, naming two well-known brands that strayed from their outdoor past. "They won't believe otherwise until I prove them wrong."

Even in hunting circles, few brands carry the authenticity of Filson. Clinton C. Filson founded the company in 1897 to outfit prospectors headed for the Klondike. He later sold clothes to the timber industry, to workers building the Grand Coulee Dam for the Army Corps of Engineers, and to generations of guides and fishermen. The Filson family sold out in 1970, but subsequent owners didn't tinker much with the products. The first outside owner had previously supplied Filson gear to independent stores in Alaska, where subsistence hunters buy their wares. In 1981, Stan Kohls, a skiwear entrepreneur, bought Filson and expanded the company's line to almost 250 products, designing them all himself. Kohls was so fussy about Filson's heritage that he refused to allow Velcro in its clothes.

The company's bestselling garment, the Mackinaw Cruiser, a sturdy coat of 26-ounce wool, has remained unchanged since its introduction in 1914, though the price has risen from $6.50 to $251. Consider this testimonial for the jacket in Filson's spring 2005 catalog: "I was in a severe airplane crash while working as a guide in Alaska. I suffered a broken leg [and] lower back, and I also had several fingers nearly torn off.... In that condition I lay in the snow for 11 hours at 25 degrees. If it hadn't been for your Filson coat, which kept me warm and dry, I wouldn't be writing this letter today." All Filson clothing is manufactured in the U.S. by a unionized workforce of 70 in a factory adjacent to the Seattle store. (A window lets shoppers watch the production process.)

Kohls sold out last year for an undisclosed price to Brentwood Associates, which has a portfolio of holdings that include another retail and catalog firm called Oriental Trading Co. as well as Zumiez, a Seattle-based chain of surf and skate shops. "I didn't want my legacy to be as the owner who sold the brand to the wrong people and ruined the company," says Kohls. "Doug is a Filson guy. He's an outdoorsman. And coming from Polo, he has experience in the sportswear business. We always thought there would be a market for Filson sportswear, but we didn't have the expertise to move into that area."

Williams is betting that people who own Filson hunting clothes will also buy Filson casual wear and that others will discover the brand as they learn of its reputation for ruggedness and quality. This fall Filson unveiled its Lodge line of items such as corduroy trousers, Henley sweaters, and wool-cotton-blend shirts. In addition to the single retail store in Seattle, which Filson has operated since 1897, Williams plans to open as many as 15 locations in major cities. The first will debut in 2006.

Some urbanites have already adopted Filson's Original Twill Briefcase. (Williams carried one for years at his old job, even though Ralph Lauren teased him about it and urged him to replace it with a Polo briefcase.) And some nonhunters have embraced its clothes: Filson gear was part of the Seattle grunge uniform of the early 1990s, and rapper LL Cool J ordered Filson clothes to wear in his videos. Williams is adamant, however, that he will never change the brand to follow trends. "If people want to discover us, that's fine, but we're not going to market to groups outside our core customer base of 30- to 50-year-old men. There's a danger to changing when you're discovered by another group: Once your 15 minutes of being 'in' are over, your new customers want something else, and your old customers won't take you back."

Even so, some of the changes Williams plans may strain the loyalty of Filson purists. While Kohls couldn't abide Velcro in Filson garments, Williams has refused to rule out modern materials such as Gore-Tex. "Our motto is 'Might as Well Have the Best,' " he says, "but what was the best in 1905 isn't necessarily the best today." This fall the company started selling a shooting shirt with a high-tech pad in the shoulder to absorb gun recoil. The pad is made from Navcom (an acronym for "noise and vibration control material"), which is used in the audio industry for studio insulation and in golf clubs and archery bows to reduce excess twanging. Williams has also raised the possibility of moving some of Filson's sewing overseas, which could lower manufacturing costs but anger the buy-American demographic that makes up much of Filson's clientele.

There is some precedent for what Williams is trying to do. On his desk in Seattle, he keeps a copy of the 1967 Eddie Bauer catalog, as both an inspiration and a caution. Outdoorsman Eddie Bauer opened a store, also in Seattle, in 1920, and for the next 51 years the company made its name with expedition-quality parkas, sleeping bags, hunting clothes, and leather flight jackets for the Army Air Corps. But in the mid-1970s General Mills bought the company, opened mall-based stores, and started selling "outdoorsy" casual wear. Although Eddie Bauer achieved peak sales in the late '90s, it has struggled lately, in part because of the introduction of Gap-like career clothing five years ago, a move that alienated loyal customers.

Peter Mathiesen, gear editor of Shot Business, a trade magazine, points to Columbia Sportswear as a company that crossed into the mainstream without alienating fans. "You see Columbia stuff everywhere now--ski jackets, casual clothing, T-shirts," he says. "But it started out as a maker of hunting and fly-fishing clothing. Columbia kept its core customers by producing cutting-edge clothing designed by hunters and fishermen at a very low price, thanks to overseas manufacturing. It's hard to walk away from top-quality technical clothes at that price."

Of course, some of Filson's true believers are already skeptical. One alarmed customer wrote to the "retail diary" of a website, "[Filson] will have polar fleece before long, and lots of brushed finishes, acid-washed this and that. The Lodge line? Yes, sure, clothes for wearing from the hot tub to the steam room. I'll personally give you $5 billion if manufacturing stays all in Seattle."

But Williams knows what's at stake. All he wants, he says, is some time and some trust that he knows what he's doing. "We'll see what our critics are saying a year from now," he says.