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conventional movement tensioned on a C-spring
aluminium, brass, glass, nickel plating, nickel silver, steel
This Barometric altimeter by the French firm Naudet & Cie, intended for aviation, aeronautical, or engineering use and manufactured in the first third of the 20th century, represents a purely functional measuring module. Naudet (PHBN/Naudet) is one of the firms that very early introduced aneroid altimeters into two “new” environments: first as altitude-indicating barometers for automobiles (around 1900), and shortly thereafter as specialized built-in aviation instruments characteristic of the First World War era.
The altimeter is defined by a distinctly utilitarian, instrumental design. The central mounting stud on the rear indicates that the instrument was intended to be installed in a cockpit panel or technical board, mounted in a holder, or used as a removable module. This points to several plausible contexts of use: early aircraft (especially military), training rooms and auxiliary instrument panels; aeronautical applications for rigid airships of the Zeppelin type and tethered observation balloons; transport and technical systems, possibly as part of integrated navigation or measurement assemblies; and, in some cases, mountain engineering equipment, elevator testing installations, or other industrial measurement setups.
The altimeter has a circular form and is housed in a nickel-plated stainless steel case, turned on a lathe from a solid billet. The case exhibits a strict, utilitarian geometry with sharply defined edges and a carefully finished surface, clearly indicating industrial use as part of a technical installation or panel.
On the front is a rotating knurled bezel that provides a secure grip. The bezel performs two functions simultaneously: it carries the altitude scale and secures the domed mineral glass protecting the dial.
The dial itself is made from an aluminum plate coated with a deep black lacquer, creating a high-contrast background. The markings and inscriptions are rendered in silver, with clear, restrained graduations and pointer-style indicators for threshold values. At the top appears the inscription “Made in France” and “ALTIMÈTRE”, while the lower portion bears the manufacturer’s mark Naudet & Cie, Paris. The altitude scale on the bezel is made of the same material and is stylistically matched to the dial, forming a visually coherent and functionally legible whole.
Notably, the scale is not labeled in meters or feet. This is characteristic of relative altimeter scales, where the change in altitude—rather than absolute height above sea level—is what matters. Such instruments were calibrated for a specific task or system. The empirical scale here functions as an indicator of relative pressure change, a visual amplifier of trend (climbing or descending), and a marker of danger thresholds rather than absolute values. For the pilot, the critical questions were: Am I climbing or descending? How quickly? Am I approaching a dangerous regime?
In the early aviation era, the very concept of an exact “height above sea level” was highly conditional. Atmospheric pressure depends not only on altitude but also on weather, temperature gradients, fronts, and local barometric anomalies. For early airplanes and airships operating at relatively modest altitudes while traversing regions of differing pressure, an altimeter with a numerical scale in meters would have been systematically inaccurate and potentially misleading. The instrument could indicate a “climb” where the aircraft was actually flying level—and vice versa.
For example:
This is a scale of aircraft behavior rather than geography. That is precisely why a relative, empirical scale had greater practical value than a pseudo-precise metric one. Such a scale acts as a visual amplifier of trend—as a marker of dynamics rather than a measuring ruler. In this sense, the Naudet instrument is philosophically closer to a variometer than to a modern barometric altimeter.
This sharply distinguishes it from tourist, mountaineering, and geodetic altimeter barometers with meter- or foot-based scales, which appeared earlier and became widespread. Those instruments were designed for a static task: determining the difference in elevation between two points under relatively stable weather conditions.
For aviation—especially early, experimental aviation involving airships and the first airplanes—such an approach was unsuitable. There, interpretive stability mattered more than numerical exactness. Thus, this altimeter is a logically coherent instrument of its era, reflecting a deep understanding of the atmosphere as a variable medium and of flight as a dynamic process.
At the core of the altimeter’s operation is a barometric movement typical of Naudet, featuring a nickel-silver aneroid capsule tensioned against a C-shaped spring; motion is transmitted to the pointer arbor by means of a fusee chain.
This altimeter should be regarded as a characteristic product of the early 20th-century instrument-making culture, oriented toward modularity, panel integration, and clarity of interpretation. It reflects a mindset in which a measuring instrument was no longer conceived as a standalone object, but as a component within a system—whether a panel, an installation, or an operator’s workstation. In this sense, the Naudet instrument serves as an indicator of the transition toward functional modules designed for practical use in complex technical environments.
