The Schlumberger unit NPTest, a provider of semiconductor testing equipment, filed for an initial public offering to raise as much as $575 million. NPTest filed with the US Securities and Exchange Commission to register common stock to be sold by Schlumberger, the world's biggest oilfield services company, and by the San Jose, California based unit. NPTest did not disclose the number of shares to be sold, the offer price or the stake that the parent group will retain. NPTest plans to use the money from the offering for general corporate purposes, including sales and marketing, administration, product development and possible acquisitions. The company will not receive any proceeds from the shares sold by Schlumberger. Goldman Sachs, Salomon Smith Barney, Lehman Brothers and Morgan Stanley will underwrite the stock sale. NPTest has applied to list its share on the Nasdaq Stock Market under the ticker NPTT.