VeriSign shares fell on Tuesday after Warren Buffett's Berkshire Hathaway sold nearly one-third of its stake in the internet infrastructure and domain name registry company for $1.23 billion.

The price of the offering hasn’t been set yet but it could raise $1.2 billion based on Verisign’s stock price in after-hours trading.

Its stock is still reasonably valued relative to its growth potential. Image source: . Berkshire hasn't bought or sold any shares of American Express since 2012. Let's see why Buffett considered it to be such a reliable long-term investment -- and why it's a great place to park a fresh $1,