When Berkshire loaned $3 billion to GE in a massive vote of confidence at the height of the 2008 credit crisis, the fund got five-year warrants giving it the right to buy almost 135 million shares of GE at $22.25 each.
Then in February of this year, GE quietly revealed an agreement to modify the deal by making it a "net share settlement."
(Read more: Buffett: Debt limit shouldn't be political weapon)
Rather than have Berkshire spend $3 billion to buy the stock and then sell or hold onto it, GE agreed to give Berkshire stock that's worth as much as Berkshire would have realized by exercising the warrants and then immediately selling the shares.
It's a smaller stake, but Berkshire doesn't have to put out any cash for it.