Bimetallic pocket thermometer having 2¼” open centre enamelled dial, twin scales, divided to 10ths, reading Reaumur and Fahrenheit scales with ranges from -30 to +40 and 38 to 122 degrees respectively. The lower part signed by the maker “Johann Holtzman.” Blued steel double-ended pointer bridging both scales at 180 degrees. Fine curved crystals to front and verso.

Finely executed rack and pinion movement, semi-circular steel over brass bimetallic strip, blued steel screws. All set within a detailed engine-turned silver band case with extension post and suspension ring.

The whole presented in its original fishskin over timber, pale mint and cream silk lined case, hook and eye catch.

A study in fine making and elegance of construction. Very few of these instruments appear, probably in the main for their fragility – once dropped almost certainly ruined, the crystals and the very fine silver band case being particularly vulnerable. This would not have been an inexpensive piece in the first place and, although it is not known how many were produced, numbers are likely to have been modest. A very similar example is to be found in the collection of the National Museums Scotland – although the Museum’s catalogue entry suggests a date of manufacture of around 1775, we feel that the correct date for these two particular pieces is c1840-1850 as another earlier example we have seen has a typical Georgian-style bow and suspension post.

The subject of conservation and careful inspection, the pocket thermometer responds well to temperature change. The dial in good original and undamaged condition, the crystals without chips, very minor hazing and some light scratches to verso. The silver case without distortion or damage. The transport case structurally sound with good colour, minor wear, losses and abrasions, some play in the hinge. The fabric interior, generally stained and faded though remaining intact.

Very much a collector’s piece.