A bistoury cache (literally “hidden knife”) used in the days before anaesthetic for urology procedures such as opening the bladder to remove stones. They were not the exclusive remit of urologists and some (of varying design) were also used for opening anal fistulae and doing hernia operations.

This is a fine example in pristine condition. The blade and handle spring are made from high quality steel and are secured to the ebony handle with gilt mounts. There is an adjustment screw with graduated markings to control the depth to which the blade can open.

• From the Phisick collection