Alnor Dew Pointer, 7300D, nonfunctional, but beautiful decorative piece

Description

The family of Alnor Dewpointers provide a wide selection of unusually precise instruments for determining the dew point temperature of air, heat-treating atmospheres or process drying gases. The maximum range of temperatures that can be measured are from about 10oF (5oC) below room temperature to about -80oF (-60oC). The actual limits depend on the type of instrument, the nature of the gas or atmosphere, the presence of Radium 226 or Americium 241, and the initial temperature of the gas within the fog chamber.
The 7300-D Dewpointer resembles the 7300 instrument in all respects except that its manometer block is hollowed out behind the liquid column to accept the detachable scales. There are two special knurled screws to hold each scale in place. One of the scales is marked in units of pressure ratio and when it is installed, the 7300-D is used in exactly the same manner as the 7300. The other three scales are marked directly in Fahrenheit.
The manual and further details can be found here:
http://www.dickey-john.com/_media/an_a_AlnorDewpointer_manual.pdf