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Rotor Enigma ← Enigma G
Enigma G31 used by the Dutch Navy
Enigma G219 is an Enigma cipher machine model G31
— also known as a counter machine —
manufactured in 1938/39 by Heimsoeth und Rinke (H&R)
in Berlin (Germany) for the Dutch Navy.
In total, the Dutch Navy had at least 93 counter Enigma machines
of the models G31 (Ch.15a)
and the interoperable A28 (Ch.15).
They were the largest Enigma G customer outside Germany [1].
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The G219 was part of a batch of at least 27 Enigma G
machines sold to the Dutch Navy in 1938 or 1939, just before the outbreak of
World War II.
It was supplied by N.V. voorheen Ruhaak & Co.
in The Hague — the Dutch representative of ChiMaAG and
Heimsoeth und Rinke (H&R). 1
The machine was found without its wooden transit case, as shown in the image
on the right. At the right is a makeshift hole for a power cable.
It was probably added by the Dutch Navy in the 1950s or 60s, as more devices
with this type of hole have been found in Dutch museums.
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Inside the machine, the battery compartment is
missing. It was probably removed at some stage after the batteries had been
leaking. Although it is our intention to reproduce the battery box,
it isn't a game breaker, as the machine can be used without it.
All three cipher rotors (I, II and III) and the reflector (UKW) are present
and have the same serial number as the machine.
When the machine was found, it was partially dismantled and some of the screws
were missing from the outer case shell. The machine has meanwhile been restored,
and is fully operational again.
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When the G31 was introduced in 1931, the name of the company was
Chiffriermaschinen AG (ChiMaAG). It was succeeded in 1934 by
Heimsoeth und Rinke (H&R). As the G219 was supplied in 1938 or 1939,
H&R was the manufacturer.
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The Dutch Navy purchased the first six counter machines
— Enigma model A28 —
in 1928 [1]. These machines had the same size as a
'regular' Enigma
and the rotors were of 'normal' size. In 1931, shortly after ChiMaAG
introduced the Enigma G31,
the Dutch Navy ordered one of the new smaller
machines, G 128, probably for evaluation and for testing the compatibility
with the A28.
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It was not until 1938 however, that more Enigma G
machines were ordered.
Divided over several orders, the Dutch Navy purchased at least 81
Enigma G machines between 1938 and 1940.
The last 6 machines arrived on
9 May 1940, one day before the German invasion of The Netherlands.
It is likely that these 6 machines (and possibly others as well)
were subsequently confiscated by the Germans.
During the war, the Dutch Navy operated from the UK, and the
Enigma G machines
were used aboard ships and submarines. After the sinking of two submarines —
O-13 in June 1940 and O-22 in November 1940 — they were no longer
used aboard submarines and were redistributed to other Dutch Naval units
operating in British waters [1]. It is likely that G219 was part of it.
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After the war, the Dutch Navy reused the surviving
Enigma G machines,
as becomes evident from the maintenance booklet of another
Enigma G of the Dutch Navy, with serial number G221 [3]. 1
The machines were used aboard ships for communication with the Dutch Antilles
and the Dutch East Indies.
According to this booklet, the machines were used until at
least 1955, after which they were replaced by modern equipment.
They were retained as spare units until the mid-1960s.
In the mid-1970s, the Dutch Navy ordered all remaining Enigma G
machines to be destroyed and discarded [2].
A few units escaped demolition and ended
up in the collections of the Dutch Naval Museum (MDH)
and the Dutch intelligence service BVD (later: AIVD).
It is unknown how and why the G219 survived,
but it is likely that it was given as a farewell present to a Naval officer
on his retirement. After his death, it eventually became part
of the Crypto Museum Collection.
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The G221 is currently held in the internal collection of the Dutch General
Intelligence Service (AIVD).
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The G219 was supplied to the Dutch Navy with the standard commerial
wiring of the rotors and the UKW. For a long time, it was assumed
that the Dutch Navy had rewired the wheels before using the machines
in an operational context, but evidence suggests that this was not the case.
So far, all
Zählwerk Enigma machines (A28 and G31)
that were used by the Dutch Navy
had the standard commercial wiring when they surfaced in the post-war
era. This means that the Dutch Navy could have been an easy target
for US and British codebreakers, both during and after WWII.
It also means that they might have been a target of the German codebreakers
during the war.
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Wheel
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ABCDEFGHIJKLMNOPQRSTUVWXYZ
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Notch
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Turnover
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#
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ETW
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QWERTZUIOASDFGHJKPYXCVBNML
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I
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LPGSZMHAEOQKVXRFYBUTNICJDW
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ACDEHIJKMNOQSTWXY
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SUVWZABCEFGIKLOPQ
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17
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II
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SLVGBTFXJQOHEWIRZYAMKPCNDU
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ABDGHIKLNOPSUVY
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STVYZACDFGHKMNQ
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15
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III
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CJGDPSHKTURAWZXFMYNQOBVLIE
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CEFIMNPSUVZ
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UWXAEFHKMNR
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11
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UKW
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IMETCGFRAYSQBZXWLHKDVUPOJN
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Below is a series of photographs that were taken during and after the
restoration of the machine. Considering its age, the G219 is in a remarkably
good condition. The die-cast bottom panel is complete and has not been
'eaten' by moisture or chemicals. Apart from the missing battery compartment
and the lamp panel hold-down nuts, the chassis is complete and all wiring
is intact.
The image above shows the machine as seen from the left rear side. It gives
a clear view of the rotors and the stepping mechanism. Note the large empty
hole in the side of the chassis, just below the rotors. In the
Ch.15b version of the machine,
this hole held a 28 contact socket/switch which could be used
for the connection of a printing device. On the Ch.15a (shown here), this
socket/switch is omitted. For a detailed description of this socket/switch,
refer to our G111 page.
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When we received the G219 in September 2022 it was in reasonable cosmetic
condition. The exterior was dusty but largely undamaged, the rotors were
present and, given its age, the lamp film was in reasonable condition.
Apparently the machine has been stored in a humid place for many years,
as there were signs of corrosion on the case shell and on the shiny metal parts.
After opening the top lid, it became clear that in the past the machine had
been taken apart. The battery compartment was missing and the wiring harness
to the lamp panel was rotated by 360°. There were no lamps present on the lamp
panel, which is usually a good thing. Over the years we've seen many lamp films
that had been damaged by installing the wrong type of lightbulbs.
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We first removed the three rotors and cleaned their exterior and contacts
thoroughly. We then traced the wiring of the rotors, to confirm that they
had not been rewired by the Dutch Navy. All rotors have the
original (commmercial) wiring.
Next, we cleaned the contacts of the entry disc (ETW) and the reflector
(UKW). We also traced the wiring of the latter and confirmed that – like
the rotors – it had not been rewired. In the next step the levers, pawls,
pinions and cogwheels of the stepping mechanism were cleaned and oiled,
after which the mechanism could be tested.
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This was done by typing on the keyboard and observing the advancement of the
three rotors and the UKW. Everthing worked as expected. Although the
original crank was missing, we checked whether it was possible to rewind the
mechanism by one or more steps, but this didn't work.
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26 lightbulbs of the correct specifications
were installed on the lamp panel and an external PSU was connected to
the machine, so that a first test could be conducted.
Only a few lamps lit up, indicating problems with the keyboard switches.
The keyboard was then dismounted from the chassis,
so that the individual switches could be inspected.
Some of the switches were misaligned and some of the
rubber pushers at the end of a key shaft were
missing or worn out. They were subsequently
replaced by new rubber pushers
that are fixated with a tiny drop of superglue.
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The rubber pushers operate the large seesaw
at the bottom of the chassis, which in turn actuates the
stepping mechanism at the rear. After mounting the keyboard back in place,
the rubber pads at the front corners of the seesaw were adjusted for
proper operation of all keys and switches.
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The sloped lamp panel is hinged and is held in place by
two screws located at the front edges of the lid.
These screws mate with a treaded brass block that is fitted to a flange on
the chassis. On the G219 these
threaded blocks were missing, as a result of which
the lid was not held in place.
It is unknown why these blocks had been removed.
Suitable replacements were made from a solid piece of brass, and mounted in
place as shown in the image on the right. The hole at the centre has 4 mm thread. The top lid is now properly
retained when the machine is moved around.
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In the next stage, the wiring for connection of a battery was restored.
Two era-correct wires were added:
one was connected to the lamp panel (visible
in the image above) and the other one was connected to the common rail of the
nearest switch below the keyboard.
For the time being, the two wires will be fed out through the
makeshift hole
at the right side of the machine. They will later be connected to a
replacement battery compartment as and when it becomes available.
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- Wooden case missing
- Battery compartment missing
- Crank missing
All lightbulbs missing Mechanism misadjusted Rubber pushers in keyboard worn out or missing Crank won't turn mechanism back - Celluloid windows above wheel missing
Lamp panel hold-down nuts missing Several screws missing from the outer case
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Device Cipher machine Brand Enigma Model G31 Designator Ch.15a Serial number G219 Manufacturer H&R Country Germany Year 1939 (est.) Customer Dutch Navy Rotors 3 Turnovers 17, 15, 11 Reflector Settable and movable (driven) Wiring Standard commercial wiring Stepping Irregular (cogwheel gear) Plugboard No Extras Crank, green sunlight filter (option) Dimensions 270 x 250 x 165 mm Weight 9.4 kg (7.2 kg without the wooden case)
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The serial number of this machine (G219) was found in the following locations:
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- Wooden transit case
- Battery compartment
- Crank
- Green filter
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© Crypto Museum. Created: Sunday 18 September 2022. Last changed: Friday, 30 September 2022 - 22:25 CET.
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