New MasterCard Stake and Secret Holdings for Warren Buffett's Berkshire Hathaway

Warren Buffett's Berkshire Hathaway is reporting a new, but relatively small, stake in MasterCard.

It's not, however, publicly reporting some "confidential information" on its just-released 13-F filing with the SEC.

As of the end of the first quarter on March 31, Berkshire reports adding 216,000 shares of MasterCard to its U.S. stock holdings.

At today's closing price of $279.15, that stake is worth just over $60 million.

Current price:

That's not much by Buffett standards and it is likely the stake was bought by Berkshire's new portfolio manager Todd Combs. He specializes in financial stocks.

Berkshire also reports a miniscule reduction in its holdings of ConocoPhillips, selling just 8,000 shares, a change of -0.02748 percent. Current price:

But that's not the whole story. The filing notes that some information has been omitted from the document released to the public. Buffett's Berkshire sometimes asks for, and receives, SEC permission to keep some holdings secret, usually as the company is building a stake. That's designed to discourage copycat buyers who could drive up the price of Berkshire's future purchases.

Current Berkshire stock prices:

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Class A:

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