Isadore Rosenthal, 99, a retired Navy machinist, apartment manager and longtime Mason who was "grand lecturer" of the Grand Masonic Lodge of Washington, died of congestive heart failure June 14 at Sibley Memorial Hospital. He was a patient at Carridge Hill Nursing Home.

Mr. Rosenthal was a Washington native who worked at the Naval Gun Factory for 37 years. When he began there, he helped make torpedoes. Toward the end, he was working on rocket launchers.

After he retired in 1955, he managed apartment buildings for developer Abe Pollin. These included the Crestwood on 16th Street NW, from which he retired again in 1982.

Mr. Rosenthal, a 33rd degree Mason, was past master of the Washington Daylight Lodge and a member of Beth Ami Congregation in Rockville.

His wife, Sarah Rosenthal, died in 1997, shortly after they celebrated their 75th anniversary.

Between 1989 and 1997, The Washington Post published several stories about the phenomenon of their long-lasting marriage.

They stayed happy, they told interviewers, because they were never bored with each other, and they liked to do the same things.

"I think in our days when you made a commitment it was for life," Mrs. Rosenthal told Post staff writer Patrice Gaines 10 years ago. "And . . . we never go to bed without kissing."

Mrs. Rosenthal called marriage "a give-and-take affair. You can't hold animosity," she said. "There will be times you have to simply make the best of it."

"For richer or poorer, in sickness and in health: That always stayed in my mind," said Mr. Rosenthal, who met his future wife when she was 14 and married her four years later. "Besides, she's a very lovely lady."

Survivors include two daughters, Bette Gordin and Helen Kamerow, both of Bethesda; five grandchildren; and 14 great-grandchildren.