I couldn't copy the original images from the '65 and '66 issues of the News, but here are some rough sketches showing the Brenot "monkey" and a similar device, the "climbing cam".
It was suggested that the 1965 cam be used with one tied to each foot. For drops of over 20' a third cam on a seat sling was suggested. A template for building your own climbing cam was provided, and they were offered for sale for $4. I don't know the history of Gibbs ascenders, but it seems that the same basic idea has been used for almost 80 years.
click to enlarge