In simple terms: Deep value, a possible future merger catalyst and growing influence offered upside without a fixed closing date. Commonwealth Trust Company is included in the Buffett Partnership special-situations record with an evidence grade of A - named and directly described in the letters.

What Buffett saw

Buffett estimated intrinsic value around $125 per share while Commonwealth traded near $50. The bank earned about $10 per share and paid no cash dividend, so value creation did not depend on an announced transaction.

This was a patient value position with a possible catalyst. A larger bank already owned 25.5% and had wanted a merger for years, but personal factors stood in the way. Buffett thought the block could take one year or ten years to unlock - and was comfortable with either because he believed the underlying value was growing.

How the situation was meant to work

The first source of return was the gap between a roughly $50 market price and Buffett's $125 appraisal. A later merger or negotiated block sale could accelerate realisation, but the investment did not require a scheduled transaction to make sense.

A larger bank had long wanted a merger, but personal factors blocked it. Buffett accumulated about 12%, became the second-largest shareholder and later sold the block in a negotiated transaction when a better opportunity appeared.

The timeline, capital and risk

Capital disclosed: About 12% of the bank was acquired at an average price near $51 per share; it had earlier been a 10%-20% BPL position.

Time frame: About one year, 1957-1958.

There was no reliable closing date, and a merger was not assured. The exit also illustrates a practical issue for large holders: the quoted market price is not always the price available for a substantial, strategically useful block.

What happened

Outcome: Buffett sold the block at about $80 when a better special situation appeared.

What the return means - and the lasting lesson

Return record: About 56.9% simple price gain from $51 to $80; not a reported IRR.

This is not classic merger arbitrage. The discount provided the defence, while a possible merger and influence over a sizeable block supplied optionality.

This guide is educational information, not a recommendation, investment advice or a substitute for reading the underlying disclosure.