The old veterans still know the MOM 39/49 M military compass well, which was widely used in the Hungarian People’s Army. In a photograph from the 1930s, the Africa explorer Count László Ede Almásy (the “English Patient”) also appears with such a device. Younger people sometimes marvel at it and ask on internet forums what it is. Let’s find out!
The compass was manufactured from the 1930s by the GAMMA factory and later by the Hungarian Optical Works (MOM). It closely resembles the instrument originally patented in 1902 by Johann Ritter von Bézárd, which is still known today as the Bézárd compass. The “Bézard-Kompass” was quickly adopted by the Austrian Imperial Army by decree Reichs-Kriegsminister 6. Nr. 3599 ex 1908. It became popular and famous. Thanks to intense lobbying, it was later standardized in Germany and then spread widely in areas under strong Prussian influence. It was also manufactured in Italy, Russia, Denmark, and even Brazil.
Note: In Anglo-Saxon countries (and thus in NATO), the lensatic compass became more common. It was named after its distinctive rotating lens plate, which includes a sighting slit for precise alignment with landmarks. In the lensatic compass, the needle moves together with the scale, so the method for determining directions differs somewhat from that used with Bézárd-type compasses.
History
The original compasses bore the inscription “Diopter-Orientierungsbussole,” which means a magnetic compass with an alidade. The term alidade comes from the Arabic word “عضادة” (al eidada = door jamb), referring to a rotatable structure equipped with slits or perforated discs (diopters). By rotating this device, distant objects can be sighted through the slits, and their direction can be read from the alidade’s scale.
Note: In a marine sextant, the alidade is the rotating arm carrying the index mirror. In a theodolite, the entire rotating upper part—with the telescope, limb, and vertical circle—is called the alidade.
The compass currently sold under the name “ORIGINAL BÉZARD” is not identical to the model described in Bézárd’s patent. Instead, it is the improved civilian version produced by Georg Lufft in Germany, featuring a 360° scale (identical to the 64-00 division Bundeswehr version).
The original Bézárd patent described a wooden base and a metal lid. That compass was still small, only 45 mm in diameter, with 5° divisions. A key innovation was the sighting slit in the lid, which allowed aiming at landmarks. Earlier pocket compasses were watch-like devices with or without a lid and were not suitable for accurate sighting.
By 1906, a larger 52 mm version was available, with an aluminum base and finer 2° divisions. During World War I, the device began to be made from a material called Hartgummi, a hardened natural rubber. Later, Bakelite was used—this is what MOM compasses are made of.
The original Bézárd compass did not have a mirror; the first mirrored model was introduced in the 1907 catalog of the French Société des Lunetiers (SL). This early model had a glass mirror, later replaced by polished aluminum, and then by nickel-plated brass because aluminum oxidized quickly in the field. The mirror’s role is to be set at an angle of about 45°, allowing the user to read the scale in the mirror while sighting the target through the slit.
From 1913, the compass dial was painted with radium-based luminous paint for night use. Due to its danger, radium paint was no longer used during World War II, replaced by non-radioactive fluorescent paint. The drawback is that it only glows for a while after being exposed to light.
Note: There is no need to worry about radiation exposure if you own a radium-painted compass! Radium emits alpha particles, which are blocked by the glass cover, so the user is not in danger. The real risk from radium paint was to workers who made the dials, as they were in direct and prolonged contact with the material.
Early World War I compasses still had a broad, arrow-shaped paper needle. In the 1930s, this was replaced by the metal needle we know today, and the index mark attached to the mirror hinge was introduced. In 1933, Polish inventor Olgierd Jakubowski developed and patented a method for adjusting magnetic declination correction. This adjustment, located on a scale at the bottom of the capsule, could be set to local needs and fixed with a screw. The MOM version does not have this feature.
A 10 cm metal ruler, aligned with the sighting line and mounted in small side clips, also appeared as an accessory between the two world wars. Around this time, the capsule began to be filled with liquid to dampen the needle’s oscillation.
Parts of the MOM 39/49 M Compass
- Magnetic Needle: Rotates on a steel pivot; the red end indicates magnetic north.
- Rotating Capsule: Protected by a glass cover on top. Under the glass are two plates: one with a circular graduation scale and cardinal point abbreviations, and another with luminous markings at the main and intermediate directions for visibility in the dark.
- Metal Lid with Sighting Slits: When the lid is opened, the desired object can be aimed at through the slits.
- Metal Mirror: Allows the user to see the position of the magnetic needle while sighting at the same time.
- Reading Index (Metal Pointer): Located at the base of the mirror, it enables reading the graduation and setting the desired value.
- Metal Ruler: Extends the sighting line; can be mounted on two small arms that rotate around the lid screws.
- Leather Case: Serves to protect the compass.
The Scale
Although there was also a version with the standard 360° scale, these compasses were most commonly made with a scale divided into 6000 grads (vonás). The conversion is as follows:
360° = 6000 grads = 6400 mils (NATO) = 12 hours
1° = 16.67 grads = 17.78 mils (NATO)
The grad scale starts at North and increases clockwise:
- East = 15-00
- South = 30-00
- West = 45-00
- North = 60-00
The circle is numbered every 200 grads, and the smallest division represents 50 grads. This was the standard layout, but there was also an artillery version, where the North mark was placed at 30-00.
Readings from the compass are written without a unit and with a hyphen separating hundreds and tens. For example, a reading of 1234 grads is written as 12-34 and pronounced “twelve thirty-four”.
Using grads as a unit simplifies calculations. A good example is the grad formula, which allows for easy determination of the distance to distant landmarks, among other things.
The Grad Formula
In the grad formula diagram, if we substitute two known values, the third can be easily determined. In the formula:
- m represents the observable dimension of the object (e.g., its height or width) in meters. Here, the church height is about 30 m, so m = 30.
- v represents the apparent size of the object from the observation point, expressed in grads (vonás). In this case, v = 00-06.
- km represents the distance between the object and the observation point, in kilometers.
To calculate: divide values under each other, multiply those next to each other. In our case: Distance=30/06=5 km
Additional Advantages
Angle function estimation becomes simpler:
- For angles up to 10-00, the sine is approximately equal to the grad value divided by 1000; above that, sine ≈ 1.
Examples: - 30° = 05-00 → sin(30°) = 0.5
- 45° = 07-50 → sin(45°) ≈ 0.6947 ≈ 0.7 or (07-50):1000 ≈ 0.75
The simplified grad formula is based on the principle that the arc length of a circle is directly proportional to its central angle. In radians: Arc length=radius×central angle.
Original Definition
1 radian = 1000 grads (vonás).
For small angles, the arc length is nearly equal to the corresponding chord length, so linear dimensions of objects can be used instead of the arc length. Practically, this means that an observer will see a 1 m tall object at a distance of 1000 m under an angle of 1 grad.
A full circle is 2π2\pi radians = 6283 grads. For easier calculations, this value was rounded to 6000 or 6400. Over time, the grad scale evolved:
- Prussian, Austro-Hungarian, and Hungarian Army (until 1945): full circle = 6400 grads, right angle = 16-00.
- Russian, Soviet, and post-1945 Warsaw Pact armies: full circle = 60-00, right angle = 15-00.
- NATO compasses: still use 6400 grads, so today the Hungarian Defence Forces are returning to the 6400-grad system.
Usage
The use of the compass is described quite thoroughly in István Soós’s book Cserkészek térképészkönyve (Scout Cartography Book), pages 98–136.
The most important things to learn from it:
- Orienting the map (p. 124)
- Measuring a bearing in the field (p. 113)
- Taking a bearing from the map (p. 101)
- Determining your position (p. 127)
Prices, Accessories, and Typical Issues
The MOM 39/49 M compass originally came with a thick leather case, a cardboard box, and a 10 cm metal ruler. At the time of writing, a complete set in good condition typically sells for around 3,000 HUF (≈ €7.50) on auction sites, though with some luck, it can be found for as little as 1,200 HUF (≈ €3)—definitely worth that much!
I’ve seen listings for 12,000 HUF (≈ €30), but that’s completely unrealistic. This model was issued in large numbers to the Hungarian People’s Army, and also used by MHSZ clubs, Youth Guard teams, the police, fire brigade, and civil defense units (I even saw one ordered by a construction company just so their tourist group would have one for the weekend). I don’t know the exact production numbers, but according to Daróczi (1995), there were about 3,400 units in 1987–88, so total production likely exceeded 50,000 units. Even today, unused stock occasionally surfaces, keeping prices low.
On used units, the cardboard box is rarely present—it was not very sturdy, wore out quickly, and took up space, so most were discarded. The small metal ruler is also often missing, as it didn’t fit inside the leather case and was easily lost.
Common, Easily Fixable Problem
The metal retaining ring that holds the capsule in the Bakelite base often seizes up. It’s lubricated with grease that thickens over time, making the capsule immovable. If you manage to move it slightly, a bit of working back and forth may temporarily fix it. If not, gently pry the capsule upward, clean its side and the housing with WD-40, dry it, and apply a thin layer of fresh grease.
Typical and Hard-to-Fix Fault
The most common serious issue is leakage of the damping fluid, which causes an increasingly large bubble inside the capsule. Despite what some descriptions claim, the bubble is not normal—it’s a defect! This is not a tubular level.
When fluid leaks out, air and moisture enter the capsule, leading to needle corrosion over time. Rust then discolors the fluid to brown. If you really want to repair it, remove the capsule (carefully pry it upward from the edge), then flush it through a pinhole at the back using a syringe. For flushing and refilling, use odorless, pure kerosene. Seal the hole with several layers of cyanoacrylate (super glue).
Sometimes fluid leakage is accompanied by the needle sticking. In this model, the needle is not locked in place when at rest—it hangs loosely and wobbles. If it sticks to the bottom of the capsule during storage, it can become glued there. Since the capsule cannot be disassembled without destroying it, the compass is generally beyond repair in such cases and should be discarded.
Interesting Facts
The photo shows an interesting clamp, which allowed the compass to be mounted on a pole. The MOM version also has the necessary hole for attaching this clamp, but as far as I know, the clamp itself was never produced in Hungary.
References
- Compassipedia (2019): The Bézard Compass. https://www.compassmuseum.com/hand/bezard.htm
- Kojanitz László (szerk.) et al (2010).: Katonai alapismeretek. Zrínyi Kiadó, Budapest.
- Daróczi Nándor (1995): Áttekintés a katonai műszergyártás, javítás helyzetéről és minőségbiztosításának alakulásáról. Katonai logisztika. 3. évf. 3. sz. / 1995. 155-166.