Three Mellon to become 525 William Penn Place.(Mellon Financial Corp. to move in)(Brief Article)(Statistical Data Included)

Greater marketability reason for return to original name

DOWNTOWN -- When the new year rolls around, a well-known Downtown office tower will sport a new, and familiar, moniker.

Three Mellon Bank Center, the 41-story office building on William Penn Place that the bank at one time shared with U.S. Steel, will again be known to the outside world as 525 William Penn Place.

The idea behind the change is one of marketability, said James Dawson, a principal of Grant Street Associates Inc., the Downtown commercial real estate firm that handles the leasing for Mellon Financial Corp. properties.

In early 2001, more than 200,000 square feet of space in …