[CR]Beborex brakes: history and info?

My recently acquired 1950's Follis has Beborex brakes:

http://www.wooljersey.com/gallery/simonpj/Follis_1955_Forestier/ADSCF1182. jpg.html

(Four pictures of the brakes, plus elsewhere in the set you'll find photos of the levers.)

They use an additional lever-arm which slides in a groove in the side of the opposite brake arm - presumably to provide extra leverage to one arm whilst, to some extent, balancing the action of the arms by making them act against each other.

In use they do seem to provide a good amount of leverage.

Can anybody provide more information on the history and design of the Beborex brakes?

Thanks,

Wyndham Pulman-Jones
Girton, Cambs., UK.