Welcome to the final installment of "11 O'Clock Stock!" Over the past 50 days we've been searching out great investments and investing our own money along the way. If you want to keep tracking the performance of the portfolio, check out our CAPS profile, which tracks the portfolio against the market, or our portfolio site with links to each recommendation. Also, remember to keep coming back to Fool.com every day for all your investing news!

When called upon to make my first pick in "11 O'Clock Stock," I went with FedEx even though the company looks richly priced. However, the stocks I buy rarely look cheap, and I stood by my three principles of investing, all of which I believed FedEx embodied:

  1. I buy excellence, and it's never cheap.
  2. I go where the trends favor me.
  3. I hold longer than just about anyone I know, which includes 100% of Wall Street.

For today's pick, I'm standing by those three principles once again. Internet retailer Blue Nile (Nasdaq: NILE) might not look cheap, but it continues to prove its worth, and I don't see the company being displaced anytime soon.

Fast facts on Blue Nile

Market Cap

$639 million

Revenue (TTM)

$320 million

Earnings (TTM)

$13 million

Cash/Debt

$47.1 million / $0.8 million

Competitors

Tiffany & Co. (NYSE: TIF), Amazon.com (Nasdaq: AMZN)

Source: Capital IQ, a division of Standard & Poor's. TTM = trailing 12 months.

Diamonds, an investor's best friend?
Blue Nile is the Internet's leading retailer of diamonds and fine jewelry. While an online purchase might not seem like the ideal way to find expensive jewelry, Blue Nile has been very successful at cornering the online jewelry selling niche.

Blue Nile succeeds a couple of ways: First, it's very good at educating and pointing shoppers to exactly the right diamond. It has a large inventory and several areas to help shoppers learn more about purchasing diamonds and other fine jewelry. Second, Blue Nile's cost structure allows the company to undercut bricks-and-mortar rivals by up to 40% and enjoy the sales tax benefits of selling online.

Back to those three principles
At the top I'd listed three of my core investing principles, the first of which is that I buy excellent companies, and they're never cheap. That's definitely the case with Blue Nile. The company trades at nearly 50 times trailing earnings.

However, as my second principle states, I also go where the trends favor me. Despite some bumps along the way, for investors, the Internet remains the great development of our time. The best part for investors is that Internet companies aren't easily displaced. I don't think anyone will out Amazon Amazon.com, and it won't be easy for anyone to displace Blue Nile either. While Tiffany is a much larger competitor, they're targeting a different segment of jewelry. Also, their cost structure is much different than a pure-play Internet retailer like Blue Nile.

In the case of Amazon, while they offer a jewelry section of their own, buying jewelry has always been a specialized enough field that big retailers can't easily dominate it. Blue Nile's exclusive focus on jewelry and educational areas gives it a key advantage in a purchasing decision that buyers put plenty of research and time into.

Finally, when it comes to my final principle, that I hold longer than just about anyone I know, I've recommended Blue Nile twice in my Rule Breakers service. Each time, as it does now, Blue Nile looked expensive when using your traditional value measures. In spite of this, my recommendation from 2006 has outperformed the market by 36%, and my original 2004 recommendation is outperforming by 44%. I've held Blue Nile for the long haul, and I expect it to keep outperforming into the future.

Bottom line
Blue Nile is extremely effective at selling jewelry online, but its status as a specialty retailer limits its growth scope. We're not looking at a company looking to explode into a $10 billion giant. However, the jewelry market is extremely fragmented, and there's ample room to continue taking share. Not only that, but Blue Nile still derives nearly 90% of its sales from within the United States, so there are plenty of untapped markets for Blue Nile to expand into.

If you're looking for an underappreciated franchise with a solid grip on its market niche, look no further than Blue Nile.

Interested in reading more about Blue Nile? Add it to My Watchlist, which will find all of our Foolish analysis on this stock.

Previous recommendations (click here for full list of recommendations and performance):

"11 O'Clock Stock" is sponsored by Motley Fool Stock Advisor. The Motley Fool will wait at least 24 hours after this publication before purchasing shares of Blue Nile. To see an FAQ on "11 O'Clock Stock," click here.