In 1955, Paperlynen produced over 42 million paper hats worldwide with more than 25,000 different inscriptions. White Castle also created a subsidiary in 1934 named Porcelain Steel Buildings that manufactured movable, prefabricated, steel frame structures with porcelain enamel interior and exterior panels that could be assembled at any of its restaurant sites. This is the first known use of this material in a building design. The company also began publishing its own internal employee magazine, the "White Castle Official House Organ", circa November 1925 (it was originally named "The Hot Hamburger"). The bulk of the material was contributed by company personnel and consisted mostly of letters and photographs of workers, promotional announcements, 25-year milestones, retirements, and similar items of interest arranged by geographic area. "Employees could... read about the progress and innovations made by those in other areas which made everyone aware of the entire system's direction and condition." The White Castle Official House Organ was published quarterly at least through the early 1980s, and at some point was renamed "The Slider Times". The Ohio Historical Society houses an extensive archive of White Castle System, Inc. records from 1921–1991, including issues dating from 1927 to 1970 of the White Castle Official House Organ. Ingram's business savvy not only was responsible for White Castle's success but for the popularization of the hamburger. In 1933, Anderson sold his half of the Business to Ingram, and the following year the company moved its corporate headquarters to Columbus, Ohio. Co-founder Billy Ingram was followed as head of the firm by his son E. W. Ingram, Jr. and grandson E. W. Ingram III. In 1959, White Castle expanded into new markets for the first time since the 1920s. Billy Ingram, who had retired to Miami in 1958, built three White Castle restaurants there. The company closed the Florida operations in 1967 due to inefficient supply distribution. Throughout its existence, White Castle has been a private company and relied on company-owned stores. It remains privately held today, and its restaurants are all company-owned; none are franchised, except very briefly in Japan during the 1980s and more recently in China since 2017. In concurrence with its 80th anniversary in 2001, White Castle started its Cravers' Hall of Fame. "Cravers" are inducted annually based on stories written about them by another person or that the particular Craver submits for consideration. Between five and 10 stories have been chosen each year, with a grand total of 64 stories selected through the 2007 induction class.