world war ii intervened, and the zeiss slr did not emerge as a production camera until zeiss, in the newly created east germany factory, introduced the contax s in 1949, with production ending in 1951. the italian rectaflex, series 1000 went into series production the year before, in september 1948, thus being market ready one year before the contax. both were historic progenitors of many later slrs that adopted this arrangement.