This is an original trailer from "The Third Man," which is often described as one of the most famous British films of all time, but was actually an Anglo-US production, as not only was the film partly finance by David Selznick, but also starred two of Selznick's contracted artists - Joseph Cotten and Alida Valli (as well as Orson Welles as Harry Lime of course).
The British contributions included Graham Greene (story and screenplay), Carol Reed (director) and Alexander Korda ...(producer). The film was based at Shepperton Studios and the production company was Korda's London Films.
Copyright in the film passed from British Lion to EMI to Weintraub and eventually to StudioCanal in 1992.
In the USA and UK, copyright protection is granted for a period of 70 years after the end of the year in which the last "principal author" died. In this case it was Graham Greene who died in 1991, so the film's copyright will expire in 2061.
In the United States however, the film famously fell into the public domain for a few years. Before 1978, US copyright law required copyright to be renewed 28 years after first publication. Selznick had died in 1965 and renewal of the film's copyright was overlooked.
Since 1978, copyright renewal has been automatic and in 1996 the film's US copyright protection was successfully restored to StudioCanal.
The US copyright of many well known films have lapsed into public domain, including "Charade" (Audrey Hepburn and Cary Grant), Coppola's "Dementia 13," Romero's "Night of the Living Dead" and Capra's "It's A Wonderful Life ."