Prime Minister Benjamin Netanyahu may have earned several million dollars buying at a steep discount shares in a U.S. company controlled by his cousin Nathan Milikowsky and selling it three years later at an enormous profit, documents indicate.

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The affair, details of which gradually emerged this month, centers around Netanyahu’s purchase of a 1.6% stake in Seadrift Coke, a Texas-based company making products for the steel industry, for $600,000. The deal assigned a value of just $37.5 million for the entire company.

But a sale of Seadrift shares believed to have occurred not long afterward valued Seadrift at nearly 19 times that figure. The implication is that Netanyahu, who was a Knesset member in the opposition at the time, received a 95% discount on the stock when he bought it.

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Because Seadrift was experiencing problems in the years that Netanyahu held the stock, Seadrift’s valuation declined from its peak. Nevertheless, the return on Netanyahu’s three-year investment amounted to 600%.

On Wednesday, Milikowsky declined in an interview with TheMarker, Haaretz's financial paper, to provide any further details about the transactions. He described the seller of the stock to Netanyahu as a “third party” but would not identify him or her, nor would he discuss the price Netanyahu paid. Milikowsky said the figures that have appeared in the media were inaccurate but refused to elaborate.

The Seadrift disclosures come amid multiple corruption probes against the prime minister and his associates that have bedeviled his re-election bid ahead of Israel’s April 9 vote. However, any investigation into the Seadrift deal will require clearance from the attorney general, which prosecutors say isn’t likely to happen before the election.

Netanyahu has declined to disclose details of the purchase, including the date or the seller. However, Seadrift was at the time led by Milikowsky, who was also a major shareholder.

As to the exact timing of his share purchase, the prime minister has not commented, but on Tuesday Israel’s Channel 13 television news revealed that it was in August 2007.

That was about three months before an Ohio company, GrafTech International (previously known as GrafTech Holdings), began negotiations to buy an 18.9% stake in Seadrift.

Because it is traded on the New York Stock Exchange, GrafTech has to disclose all material transactions to the U.S. Securities and Exchange Commission. It did that, and the filing shows that Seadrift was being valued for the purposes of the deal at $715 million.

Assuming that Seadrift’s value did not suddenly jump 19-fold during the three months, the inference is that Netanyahu bought his shares at a 95% discount to their actual value.

By April 2010, when GrafTech decided to buy more shares and take a controlling stake, Seadrift was losing money and the second deal was done at a company value of about $308 million, 60% less than in November 2008. Nevertheless, Netanyahu profited enormously

Netanyahu agreed to sell his Seadrift stock to Milikowsky in 2010. Yet, in spite Seadrift’s troubles, Netanyahu was still able to profit handsomely because of the discount he had received three years earlier: The $4.3 million he received was more than seven times what he paid.

In addition, Netanyahu received dividends worth hundreds of thousands of dollars while he held the stock.

In an interview with the Channel 12 television news Saturday night Netanyahu showed that he was deeply familiar with Seadrift’s business. That makes it difficult to believe he didn’t know he was buying Seadrift stock at a deep discount.

It also belies Netanyahu’s earlier statements that he had never talked about business with Milikowsky and that he had been a passive investor who knew little about how the company was run or faring.

Netanyahu asserts that he bought the shares at market price, but Seadrift’s profits in 2007 of $60 million do not support that claim.

Neither in the steel or any other industry are companies ordinarily valued at a fraction of a single year’s profits. Thus the transaction raises suspicions that the transaction was designed to provide Netanyahu with a guaranteed profit.

In addition to suspicions concerning the share transaction, the affair may be linked to Case 3000, where investigators alleged that several Netanyahu associates profited from Israel’s purchase of submarines from the German company ThyssenKrupp.

ThyssenKrupp is one of Seadrift’s four biggest customers, according to SEC filings.

Moreover, the journalist Yoav Yitzhak reported that the person who drafted the agreement for the 2010 share sale between Netanyahu and Milikowsky was Isaac Molho, a partner in the law firm of David Shimron. One of the main suspects in the submarine affair, Shimron was also the lawyer for ThyssenKrupp’s Israeli representative, Michael Ganor.

It bears adding that no direct links have been established connecting the purchase of Seadrift shares with Case 3000 and Netanyahu’s office insists there aren’t any.

“The prosecution’s announcement that it won’t be investigating the submarines affair any further, and the German company’s announcement that it didn’t buy anything for the submarines from the company that the prime minister or his cousin were invested, are reason enough to stop prying into shares about which the prime minister reported to the authorities, and on which full tax due was paid,” his spokesman said.