Marketing has begun on the conversion of the commercial building at 31 East 28th Street to condominium apartments.

The project is being developed by Henry Justin of HJ Development Corporation.

The 12-story, mid-block building will have 22 apartments, two of which will be duplexes. The units will range in size from about 1,775 to 1,950 square feet and Alan Tanksley is doing the interior design.

The building was erected in 1912 and designed by Schwartz & Gross, one of the most prolific architectural firms specializing mostly in apartment buildings in the early decades of the 20th Century.

The building has a three-story limestone base and a beige-brick facade divided into three bays of two double-paned windows each. The building has an attractive stringcourse above the third floor and the spandrels have attractive masonry designs and the base of the window sills have elaborate designs.

The building, which has a canopy entrance, a small lobby and an elevator, is directly across the street from the entrance to the Ziff-Davis office building and it is close to many of the area's finest buildings including the gargoyle-clad 95 Madison Avenue, the recently opened Carlton Hotel on Madison Avenue between 28th and 29th Streets that has a popular restaurant named Country, and the Met Life and New York Life Insurance Company towers on Madison Square Park, two blocks to the south. There are several other conversions underway nearby.

Mr. Justin's other conversion projects have included the Cass Gilbert condominium at 130 West 30th Street and the Heywood at 263 Ninth Avenue at 26th Street.

The marketing for the project proclaims "Live in a New Golden Era," adding that "Passage doors with ribbed glass transoms and cabinetry with polished nickel bullet hinges harden back to New York's heyday, when luxury was defined by classic detailing and the finest materials."