This letter and the accompanying cue sheets for El Cid were provided by John Wallington of Ontario, Canada. Other than the formula for calculating "curtain feet", the instructions provided were identical to the 70mm roadshow run.
Allied Artists began life as the Monogam Studio, in the early silent era. By the time television had severely impacted the film industry, Monogram's grade Z product no longer could find a home on theatre screens and the company reorganized its operations and became Allied Artists. Like the similarly named United Artists, they didn't really make movies any longer, instead they distributed the product of independant producers. While much of what they handled was still pretty low grade, there were outstanding exceptions, such as Walter Wanger's Invasion of the Body Snatchers and William Wyler's The Friendly Persuasion. El Cid was their first full blown epic and huge money maker. AA handled the distribution of the film only in the Western hemisphere, while the Rank Organisation distributed the film in Europe.
The letter below, explaining that there was only one copy of a radio promo record in existance, gives you a pretty good idea of how Allied Artists compared with the major studios. Their modest finances didn't alter the desire for proper showmanship, as is seen in the cue sheets that follow.