Apartment 10B at 25 East 83rd Street provides a generous and flexible floor plan, bright eastern views, and an unparalleled location on the Upper East Side, all within a full-service, modern-style cooperative, built in 1938.    The apartment overlooks Madison Avenue, and is currently arranged as a "Junior 1-bedroom," but can also function as a large alcove studio with a separate kitchen, dining area, and full dressing room. While the current layout offers privacy, functionality and additional storage, re-arrangement possibilities for this layout are plentiful.    Throughout the apartment, generously proportioned windows serve as focal points, with eastern exposures just above the view break in the living room, large bathroom, and separate kitchen. The apartment's unique layout creates a panoramic view, stretching north along Madison Avenue.    Residents of 25 East 83rd Street enjoy a highly sought-after central location on the Upper East Side -- a block from the Metropolitan Museum and Central Park -- and minutes from the 86th St corridor with a bevy of supermarkets and shopping, along with the 4, 5 and 6 subway lines on Lexington Avenue. The building has a full time doorman, live-in superintendent, and a fitness room. 75% financing is allowed, and there is a 2% transfer tax. Pets and pied-a-terres are also allowed.    25 East 83rd Street was designed by the influential Fredrick Lee Ackerman, an architect with experience ranging from regional housing planning to individual country homes. Ackerman's significant innovative features like the building's chamfered corners, generous window proportions, and central air systems were precursors to the mid-century designs seen decades later the "post-war era;" and such elements have a direct effect on these distinctive apartments. In fact, Ackerman loved the building so much, he decided to move in and call it home himself.