The following video is part of our "Motley Fool Conversations" series, in which consumer goods editor and analyst Austin Smith discusses topics across the investing world.

In today's edition, Austin discusses four things investors eyeing American Express should keep on their radar. At the top of his list is an "opening" or relaxing of their closed-loop model. Being a closed-loop company has been a key in their success story up until now, but it has also curbed growth a bit. Watching how they manage a slightly more open model now that they have relationships with banks will be key going forward. Mobile payments, changing demographics, and its charge-off rate are three other key trends investors need to keep an eye on. At the end of the day, American Express remains a strong company with a great business model and robust management. The continued shift towards mobile payments should benefit them in the future, and that's just one reason Warren Buffett continues to own AmEx in his Berkshire Hathaway portfolio.

The financial heavies like American Express are getting a lot of press these days. But there's one small finance stock that's flying under the radar. It has some of the best operational numbers you'll ever see. The Motley Fool featured it in our brand-new free report: "The Stocks Only the Smartest Investors Are Buying." We invite you to download a free copy. To find out the name of the bank Buffett would probably be interested in if he could still invest in small banks, just click here.