In yet another sign of the apartment market's strength, a venerable building on Seattle's First Hill sold this week — for twice the price it fetched a year ago.

The Marlborough, a 1927 building at Boren Avenue and University Street, was sold for $26.7 million by Trinity Real Estate of Seattle and Helix Funds of Chicago to an entity whose backers could not immediately be identified, public records show.

The Trinity/Helix venture paid $12.75 million in September 2010 for the 12-story building. The seller then was a bank that had foreclosed on the previous owner, whose plans to convert the Gothic Revival building to condos were cut short by the housing crash.

Trinity principal Richard Leider said his firm and Helix spent $3 or $4 million renovating the 83-unit building, then put it back on the rental market in January. It was fully leased by midsummer, he said.