The long-anticipated sale of the Index, Portfolio and Risk Solutions (IPRS) business kicked off in early June, and several bidders recently progressed into the auction's second round, the people reported.

Before Barclays provided detailed financial information on the index business, potential bidders had estimated the unit to be worth above $400 million, the people said. The business includes a basket of over 98 major indexes, according to the unit's website.

But the business showed much higher than expected revenue figures during early due diligence, and now potential buyers are valuing the unit at nearly $1 billion, the people said, asking not to be named because the matter is not public.

The estimated price tag reflects a multiple of over eight times revenues, which is in line with precedent transactions for index businesses, the people said.

A Barclays representative declined to comment.

The U.S. Aggregate Bond Index, which Barclays bought as part of the Lehman Brothers acquisition during the financial crisis, is among the platform’s best-known offerings.

In addition, the Barclays business includes a risk solutions software tool used by institutional investors to perform analysis of their holdings.

Indexes such as MSCI Inc, London Stock Exchange Group Plc, McGraw Hill Financial's Standard & Poor's index unit, as well as financial information services Markit Ltd and Bloomberg LP could be contenders, one of the people said. It was unknown who still remained in the process.

Barclays also had attracted preliminary interest from Interactive Data Corp and Thomson Reuters Corp.

Reuters first reported in November that Barclays began exploring options for the index business following an approach from MSCI.

Northwestern Mutual Life Insurance Company recently sold its index business, Russell Investments, to the London Stock Exchange Group Plc for $2.7 billion.

(Reporting by Mike Stone; Editing by Leslie Adler)

By Mike Stone