More than 50 years later, mid-century modern design remains both relevant and fascinating. Here, author Jenna McKnight selects eight pieces that have been in production ever since they were designed in the 1950s and 60s. These works have not only influenced generations of designers but have also remained popular themselves, staying in continuous production for decades. "Mid-century modern (MCM) is one of the most enduring design styles in history," said McKnight, a Dezeen contributor whose new book Design: Mid-Century Modern tracks the development of the style. "I live in California and see examples of MCM every day — in homes, offices, libraries, museums, and beyond. Even my dermatologist has mid-century modern decor in her office, from the Barcelona Chair to the Panton Chair," she told Dezeen.…