In a deal potentially worth more than $57 million, Yale will sell slightly less than half of the shares it owns in Acadia Realty Trust in an offering expected to close today, the investment trust announced last week.

Yale currently holds about 8.8 million common shares in Acadia, a real estate investment trust. Under the plan announced March 22, the University will sell between 3.6 and 4.2 million of those shares in a secondary public offering for a price of $13.75 per share.

When the investment first appeared on a form the University filed with the Securities and Exchange Commission, Acadia shares were worth only $5.69 per share.

According to the most recently filed version of the same form, Acadia was by far the most valuable investment Yale held in its own name on Dec. 31, 2003, the period covered by the document. Yale owned more than 8.8 million shares worth approximately $110.3 million. The next most valuable investment held by the University, shares of Morgan Stanley, were worth about $67.9 million.

Yale President Richard Levin and University spokeswoman Helaine Klasky both said they had not heard of the sale and, as a result, could not comment on it. A representative of the Yale Investments Office declined to comment on the offering.

Acadia is not directly involved in the offering and will not profit from it, Acadia Vice President Jon Grisham said Tuesday.

“The company does not get any cash, it’s just a rotation of shareholders,” Grisham said.

He said Acadia owns and operates 62 properties with a total size of nine million square feet. Most of these are grocery-anchored shopping centers in the North East or Midwest, according to the trust’s Web site. Acadia owns no properties in New Haven, but it owns two centers in Connecticut — one in Greenwich and another in Rocky Hill.

Before the sale was announced, Yale held about 32 percent of the company’s stock. It will now have approximately 17 percent.

A total of five million common shares are being sold in the offering, with Acadia’s former chairman Ross Dworman selling the other 1.4 million shares, according to an Acadia press release. Grisham said the fact that both Yale and Dworman are selling at the same time is coincidental.

Grisham said the total size of the sale will depend on the offering’s underwriters.

“Anytime you have a public offering, the underwriters have an option to offer an additional 15 percent of the initial offering amount,” Grisham said.

Yale is initially offering 3.6 million common shares but could add up to 591,386 additional shares if the underwriters exercise their option, according to an Acadia press release.

This is the first time there has been a secondary offering of Acadia shares, Grisham said.

Each quarter, the University is required to file a 13F-HR form with the SEC listing the stocks it holds in its own name. The form only lists the stocks held on the filing date and does not include investments controlled by outside managers, which constitute the vast majority of Yale’s assets.

Yale’s August 2000 filing for the quarter then ended in June of that year was the first to list Acadia as an investment, in the form of about 3.4 million shares worth $19.1 million. By the November 2000 filing indicating stocks from September, the investment had grown to 6.1 million shares worth $36.4 million.

The price of Acadia stock has risen rapidly over the past four years. At close of business Wednesday, Acadia shares were trading for $14.05 a share.