When the staff of One Potato. Two Potato announced the last call shortly before 1 a.m. this morning, they took the last orders the business will accept for more than a year.

The restaurant and bar marked the temporary halt in 10 years of business on the Square with a half-price drink sale. It became the third shop to shut its doors for the construction of a new five-story retail-office building.

Three more stores will temporarily close by Saturday, in preparation for the demolition of most buildings on the Mass Ave block between Plympton and Linden Streets. Briggs and Briggs Music Shop, which is in a building owned by the Harvard Club of Boston, will be the only business on the block not affected by the construction.

Plans for the new building call for converting the present storage area into a 34-car private garage, extending the backside of the structure into the existing open-air private parking space behind Mass Ave to create additional office space, and designating the groundfloor space for four retail stores.

Claus Gelotte's Camera Shop, Stonestreet Clothiers, Bob Slate Stationer and One Potato, Two Potato are expected to move into the retail spaces. Games People Play will not return to the Square, says Carol Monica, the shop's owner.

Gelotte's manager Antonio R. Tucci predicts that the new building will bring an upswing to his business. "1985 is when the 'T' should be done, and we will come into a new building," he explains, adding. "It could be a turn-around time for Harvard Square."

But other Square businessmen are less sanguine about the development. "When they tear the old building down, a little of me will go down with it....[Gelotte's] has been a landmark for 45 years," says John Penney, who worked for Gelotte's for 14 years and is now manager of Ferranti Dege Camera Shop across the street.

Agrees Bob Slate, founder of the 50-year-old stationery store: "A five-story building with a garage underneath, yech."