By Stephen Wilmot

Exor is sometimes seen as the European Berkshire Hathaway. The comparison is imprecise, but the listed investment vehicle of Italy's Agnelli family still seems a rare bright spot in the global car industry.

The most attractive thing about Exor is its record: Since March 2009, when the company was formed out of various legacy Agnelli holding companies, shareholders have made roughly nine times their money. That compares to a little over five times for the S&P 500 index and less than four times for MSCI World, which Exor uses as a benchmark.

The problem with that record, unlike Berkshire's under Warren Buffett, is that it isn't unambiguously the work of Exor's 44-year-old chairman John Elkann. Much of the value was created at Fiat, the company founded by his ancestor Giovanni Agnelli, notably through its 2009 partial acquisition of Chrysler out of bankruptcy. The 2016 spin off of Ferrari, which now fetches a high luxury-sector valuation, was another big contributor. Both moves at the time seemed masterminded by the late Sergio Marchionne, who died in 2018.

Yet Mr. Elkann is on his way to proving his own financial discipline, including in the coronavirus pandemic.

In early March, he agreed to sell PartnerRe, an insurance company Exor bought for $6.9 billion in 2015, to French insurer Covéa for $9 billion. As stock markets plunged, Covéa tried to renegotiate. Mr. Elkann stood firm and the deal collapsed last month. Although it is a shame Exor missed out on a profitable exit, it was always a reluctant seller. Mr. Elkann's refusal to buckle under pressure is paying off in the case of another big deal.

In December he agreed to merge Fiat Chrylser, of which Exor owns roughly 29%, with French peer Peugeot. The terms were favorable to Fiat, notably because of a EUR5.5 billion ($6.1 billion) special dividend due to its shareholders before completion. That payout started to look reckless amid the cash crunch facing auto makers in the shutdowns. But again Mr. Elkann stood firm, arguing at Exor's annual general meeting last month that the deal terms were "set in stone."

The financial strain on manufacturers is now easing, and there is little sign that the car deal will go the way of the insurance one. Both companies need a merger, and Peugeot has repeatedly reaffirmed its intention to honor December's agreement (except for 2019's expected dividends, which neither company will pay). The deal should complete early next year.

The comparisons between Exor and Berkshire Hathaway are likely rooted in Mr. Elkann's 11-year habit of writing contemplative annual letters to shareholders, many of them containing quotations parsed from Mr. Buffett's own annual letters. They became more serious when he bought an insurance business. Both boast long investment horizons.

The big difference is Mr. Elkann's greater readiness to sell when he gets a good offer. A better comparison than Mr. Buffett might be cable billionaire John Malone, whose fortune was made more through complex deals and spin offs than being in an inherently attractive business. Mr. Elkann needs to sell -- and keep that EUR5.5 billion dividend in the Fiat-Peugeot merger agreement -- because he inherited a portfolio with a risky skew toward the capital-consuming automotive industry.

For now, Exor remains mainly a play on cars. That explains why the stock has fallen 27% this year and stands 22% below book value -- an unusually steep discount. Yet the company under Mr. Elkann is starting to look like a beacon of capital discipline in the sector, just as Fiat was under Mr. Marchionne. Exor could be one auto stock that takes investors to a better place.

Write to Stephen Wilmot at stephen.wilmot@wsj.com