Guy Spier (Aquamarine Zurich AG) – Q3 2025 13F Portfolio Review

In the most recent 13F filing, Guy Spier’s Aquamarine Zurich AG reported a portfolio valued at $317.37 million, with the top five holdings accounting for 77.64 % of total assets.

A disciple of Warren Buffett and Mohnish Pabrai, Spier continues to run one of the most concentrated and quality-focused portfolios among value investors—anchored in financials, payments, and enduring consumer franchises. Below is a detailed look at the fund’s top positions this quarter.

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Berkshire Hathaway Inc. (CL B) – 22.27 %

Spier’s largest holding remains Berkshire Hathaway B shares, representing 140,600 shares valued at $70.68 million (22.27 % of assets). The position was unchanged this quarter, underscoring Spier’s deep admiration for Buffett’s capital-allocation discipline and the conglomerate’s blend of insurance, industrial, and energy earnings. It continues to serve as the portfolio’s core long-term compounder.

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American Express (AXP) – 21.98 %

The fund holds 210,000 shares worth $69.75 million (21.98 %), also unchanged from the prior quarter. Spier has long favored American Express for its powerful brand, closed-loop payment network, and high-return business model. This enduring stake reflects his belief in owning world-class franchises with durable moats rather than trading around short-term market noise.

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Bank of America Corp (BAC) – 12.48 %

Aquamarine’s third-largest position is Bank of America, totaling 767,845 shares valued at $39.61 million (12.48 %). The holding remained steady this quarter, suggesting continued confidence in BofA’s deposit base and cost discipline. Like Buffett, Spier appreciates the bank’s long-term earnings power through economic cycles.

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Mastercard Inc. (MA) – 11.78 %

With 65,750 shares valued at $37.39 million (11.78 %), Mastercard anchors Spier’s exposure to the global payments ecosystem. No changes were made during Q3. The position highlights his preference for asset-light, high-margin businesses benefiting from secular growth in digital transactions and network effects.

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Ferrari N.V. (RACE) – 9.13 %

Rounding out the top five is Ferrari, with 60,000 shares worth $28.98 million (9.13 %). The luxury automaker’s pricing power and scarcity appeal fit neatly within Spier’s long-term quality framework. Ferrari’s ability to compound free cash flow and maintain exclusivity resonates with his Buffett-inspired philosophy of owning “the best business you can find and holding it forever.”

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Other Holdings

Smaller positions include Micron Technology (MU) at 4.22 %, Moody’s Corp (MCO) at 4.05 %, and Alibaba Group (BABA) at 2.68 %. The only notable move this quarter was a 60 % reduction in Micron Technology (-120,000 shares), signaling selective trimming amid semiconductor volatility, while a modest increase in Core Natural Resources (CNR) (+32.6 %) added incremental upside in natural-resource exposure.

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Conclusion
Aquamarine Zurich AG’s Q3 2025 portfolio exemplifies Guy Spier’s hallmark concentration and quality bias. With over 77 % in just five holdings—spanning Berkshire, American Express, Bank of America, Mastercard, and Ferrari—Spier continues to favor businesses that compound intrinsic value through strong brands, durable economics, and shareholder-oriented management. Rather than chasing fads, his disciplined patience and focus on enduring franchises remain the cornerstone of his long-term investing success.