WASHINGTON, DC—This past summer Boston Properties CEO Owen Thomas told shareholders during the REIT's second quarter earnings call that it had a domestic buyer under contract for a 325,000-square foot CBD office at 505 9th St., NW (the building's alternative address is 500 8th St., NW).

He told listeners the amount ($318 million) and the price per square foot ($977) and the forward NOI cap rate (4.4%).

He didn't reveal the buyer, however. Now we know: Prudential Real Estate Investors acquired the 10-story office property on behalf of institutional investors.

We also know the reason following the company's statement on the deal, although frankly this we could have guessed. "With an improving employment outlook and the expectation that tenants' flight to quality and amenities will continue to drive long-term demand for premier office product in the East End, 500 8th Street is well-positioned to generate strong and stable cash flows for our investors," Kevin R. Smith, head of Americas for PREI, says in a prepared statement.

With the mystery buyer revealed and the deal actually closed -- after all a deal under contract still can fall apart -- we can now focus on the second part of Owens statement to shareholders. Namely, that the property really traded for more than $1,000 per square foot.

His reasoning: The buyer is assuming $117 million of above market debt which when factored into the valuation, brings the price to in excess of $1000 per square foot and an even lower effective yield.

As of its Q2 earnings report, Boston Properties has either completed or contracted for total dispositions of $377 million and remains on track for targeted total dispositions of $750 million for 2015, Owens said. The REIT is recycling the capital into newer projects.