WARWICK, Bermuda (Reuters) - New Zealand businessman Eric Watson has added two "blank check" companies to his investment portfolio, filing with regulators yesterday to raise a combined total of up to $1.5 billion.

Mr. Watson, who is chairman of both entities, earlier this month closed on a reverse merger of casual wear retailer American Apparel through another blank check company he formed in 2005, Endeavor Acquisition Corp.

Endeavour International Acquisition Corp. and Grand Slam Acquisition Corp., in registration statements with the US Securities and Exchange Commission, filed for initial public offerings of up to $750 million each.

Blank check companies, also known as special purpose acquisition companies (SPACs), are formed for the sole purpose of acquiring other businesses.

Endeavour is offering 75 million units at a price of $10 each. Each unit will consist of one ordinary share and one half warrant.

Each whole warrant will entitle the holder to purchase an ordinary share for $5.50.

Endeavour intends to acquire one or more businesses with principal operations located outside North America, according to the filing. It does not intend to target in the financial services, entertainment, media or publishing industries, according to the filing.

Grand Slam also intends to sell 75 million units under the same terms as Endeavour. It will seek to acquire one or more businesses with operations in North America, and will steer clear of the same industries as Endeavour.

Blank check offerings, which have soared in 2007, generally tap investors in the public markets prior to making acquisitions, and usually have an agreement to return funds to investors within a specified period if they fail to close deals.

Mr. Watson, a British resident, has since 2005 been involved with numerous blank check companies, including Victory Acquisition Corp, Triplecrown Acquisition Corp and Performance Acquisition Corp.

Edward Mathis, a managing director of private equity firm Carlyle Group has also been involved in numerous of Mr. Watson's ventures, including the American Apparel deal.

Mr. Watson, chairman of Cullen Investments, began to build up his fortune more than a decade ago when he formed a US office supply company.

Among his investments today is majority ownership of the New Zealand Warriors rugby team.

Although a number of the blank check companies formed by Watson and other investors have yet to close on acquisitions, investors in Endeavor Acquisition achieved a roughly 200 percent return on their original investment, according to a statement on Cullen's website.

Blank check companies, which have only come into vogue in recent years, have courted controversy because they have no revenue or operating history - just a management team promising acquisitions if the right opportunity presents itself.

After a slow start, these specialized offerings have raised more than $12 billion so far this year.

In comparison, blank-check offerings raised just $24 million in 2003, the first year they were floated to public investors, $480 million in 2004, $2 billion in 2005 and about $3 billion in 2006, according to data tracker Dealogic.

Increasingly the offerings are being brought to market by high profile management.

Activist billionaire Nelson Peltz and Texas businessman Tom Hicks having each launched blank check deals this year.

As the deals have become more prevalent, and more richly valued, major underwriters have signed up.

Citigroup is leading both the Endeavour and Grand Slam offerings.