A fine an and exceedingly rare example of Chambers’ which incorporates a rack-and-pinion mechanism that exerts remarkable force by means of a wing-nut while providing for a perfectly parallel relationship between its jaws which limits damage to any pedicle.  A spring-catch permits for partial or complete disarticulation of the jaws.  Originally made by Messrs. Mayer & Co., Great Portland St., London.  - Catalog of Obstetrical and Other Instruments Exhibited at the Conversazione of the Obstetrical Society of London on March 28th, 1866.