A Troughton bowfront stick barometer with ivory float of closely related design (to the extent of the finial) is illustrated in Edwin Banfield, Barometers Stick or Cistern Tube, Baros Books, 1985, p.81, fig.96.
The plates of the Banfield barometer give the customary weather indications (Fair etc) not seen on this barometer. The cistern on the present example has an ink inscription for Joseph Somalvico at his Charles Street address; a further inscription behind the left register plate also relates to Somalvico. It seems probable therefore that at some stage the plates have been changed, possibly by Troughton in order to retail the barometer.