Nice example of a Josiah Longmore silver pencil. UK patent 9719 (1843). It works similar to magic pencils, however, it is the upper external barrel that you pull on in order to extend the pencil tip. This one is in excellent working condition. It is likely an early example, given the imprint on the barrel. See pic for J. Longmore patent from 1843 – UK patent 9719.
"J. Longmore & Co’s. Patent London"