This extremely rare antique (1938 to 1961) Dewrance of London Depth Gauge for a submersible is an incredible nautical find and is calibrated in PSIG (Pounds per square in gauge pressure). The PSIG corresponds with the depth based on the pressure exerted by descending. 1 atmosphere = 14.7. For every 33 ft of depth in ocean water you will see a pressure of 1 atmosphere (14.7 psi). So 100 Ft corresponds. 44.55 PSI.
The gauge measures 48.5cm across the back and is 8.5cm high. The very thick bevelled glass front measures 39.2cm inside the casing.
Please view the pics carefully to fully appreciate this magnificent piece and to confirm the condition. There is normal age and usage related wear and tear that one would expect to find in an antique piece such as this.