The Drumm Geminy shield, Lockpicking
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The Drumm Geminy shield
My name is Han Fey and as a collector of high security locks, I am interested in the techniques behind
the security that they afford. With locks intended for extraordinary usage, these high security features
are often not clearly visible.
I take pleasure in disassembling locks and from that, learning their internal workings. I have at the
moment about 2100 different locks from all over the world.
In this article, I will discuss the security features and the technology of the Drumm Geminy shield.
Klaus Drumm, a 57 year old German, is the creator of this locking system. During his working period at
BASF in Ludwigshafen he became interested in security. He is now quite busy with developing,
analysing and improving security products. Aside from that, Klaus is also an inventor with at least 160
Patents to his credit. I have met Klaus Drumm on several occasions, and I can easily say that he is a
very pleasant and friendly person. But relevant to this article, I particularly enjoy his willingness to talk
openly and freely about locking / security techniques as well as their countermeasures. I have learned
a lot from him.
I call his Geminy shield a High Security lock as it can withstand most hostile attacks with a great deal
of success. More about that later.
The technologies that I write about in this article are based upon my observations from working with
parts of my collection. Please be advised I disclaim liability for any errors within this article’s content.
However, I have done my best to record it as accurately as possible. For errors and suggested
corrections, see the end of the document for my contact details.
The Geminy slogan is:
There is a difference between “feeling secure”and “being secure”
Geminy is the difference
Keyway (10-pin)
Frontview Geminy shield, Close, Keyway and Open
Han Fey, July 2006, Drumm Geminy Shield 1
Introduction of the Geminy shield
About 15 years ago Klaus Drumm had the idea that the small surface in front of a cylinder was not big
enough to provide for an effective Shield against differing modern burglar attacks. He wanted a
solution for this. With this idea in mind, he came to the conclusion that a cylinder shield out of steel
which could withstand several attacks could be the solution. His thinking was that such a shield would
protect the cylinder against intensive hostile attacks from the outside, such as drilling, sawing and
beating it with a hammer. Drumm’s strategy is that the main two contributors to creating a highly
secure locking system, involve increasing both the time it would take, as well as the amount of noise
that would be created, should any attempt be undertaken in order to defeat a lock like his shield.
Research in Germany indicates that these two factors play a very significant role in reducing the
incidence of burglary. This data indicates that typically, after 4 to 5 minutes without success, a burglar
tends to move on.
The steel Drumm Geminy shield is located in front of the lock’s cylinder. Its 7mm thick hardened steel
plate which is located in front of the lock’s cylinder, acts as a first line of defense against all known
break-in techniques. When this lock is installed on a door, the cylinder is not visible. This is because
the cylinder is totally shielded as you could see in the pictures before. Should a criminal succeed in
overcoming this barrier, he or she would as in the case of conventional security fittings, still have to
deal with the lock’s cylinder.
The product line of Geminy is currently the world market leader in protective fittings mounted on
machines with either considerable quantities of cash or of items of a relatively high resale value.
Specifically, this includes railroad ticket machines, charge collecting machines, automatic teller
machines and cigarette vending machines. The Geminy shield also is widely deployed within prison
facilities as well as psychiatric clinics. Pay telephones which are located in remote areas are also good
candidates for being fitted with the Geminy shield. With regards to railroad usage of the Geminy, the
German railroad system currently uses more than 10,000 of these locks. And in the Netherlands, you
can also find these locks on all of the Dutch railroad’s ticket machines.
There are nowadays more manufacturers who employ the usage of covers to protect cylinders against
vandalism etc, but the Drumm shield was in my opinion one of the first. Of particular interest is that this
lock is a 100% mechanical system. Where as other shielded locks that compete, they typically employ
the usage of either magnets or electronics.
The three way protection
This Drumm Geminy shield protects your cylinder against drilling / pulling, lock picking and vandalism.
And by vandalism I mean to say, it protects against the insertion of glue, wooden stick of a match, dirt,
sand etc. which can be inserted in the keyway of a lock’s cylinder and could potentially, impede the
unlocking process. The locking mechanism in the shield itself is protected by a self-cleaning feature.
The manufacturer supplies a Teflon spray which protects the lock for 3 months against super glue and
other agents that somebody could insert in the keyway. The shield also is secure against lock picking,
due to the specially shaped pins used in this lock. More about that later….
Drumm logo with in the front the special Teflon spray
Han Fey, July 2006, Drumm Geminy Shield 2
The key
The standard key has 5 positions, were a “key pin” can be mounted. There are 10 different key pins.
And every key pin has two different heights which control the pins in the lock. The system can
therefore be called a pin in pin system much like the Mul-T-Lock system. On the picture below you can
see some keys with different keypins. In Germany they call this key a Pfannenschluessel, this means
something like a frying pan key.
Some Geminy keys
Note: The max. key pin height is 6 mm, the manufacturer did this to make the total key not thicker than
11 mm, in order to avoid problems in the pocket of your trousers. There are 100.000 theoretical key
combinations, with 5 key pins on the key. The manufacturer claims that each individual key is unique.
Additional copies of a key are available only with a security card.
How the lock works
You can see that the lock consists of two simple sliding parts
.
I call the part that is fixed on the door
the “Body”, and the part that moves upwards and down, the “Sliding front”. This Sliding front covers
the cylinder when this hardware is locked. The 10 pins in the corresponding 5 holes prevent the
Sliding front from being moved. If the pins are pushed in properly by the key, a shear line is created,
(all the pins are on the same height as the Sliding front) and you can now move the Sliding front
downwards to open the lock.
The “Body” and the “Sliding front”
Note: The preceding picture shows this lock’s 5 chambers for the pins as well as a small hole in the
body (see arrow) which is intended to prevent the “Sliding front” from coming off. This specific lock
contains 46 parts. Furthermore, in each chamber there are 8 parts.
Han Fey, July 2006, Drumm Geminy Shield 3
To open the lock
To open the lock, you place the key with the key pins downwards on the “keyway” and push it down.
The pins are now set and it is now possible to make a sliding movement. Because the pins in the lock
are pushed in properly by the key, you can now move the slider downwards. The lock is now open and
you can remove the key. The cylinder has become visible. To close the lock, there are two possibilities
according to the specific model of the Geminy Shield. One version requires the installation of the key
in order to slide the front back into position. The second version can also be closed without the usage
of its key. In the pictures below you can see the back of the “Sliding front”, with some different keys in
it. Of course, normally the pins in the body (top pins) block the Sliding front from sliding.
Shear line in back of Sliding front in locked position
Note: This picture is from the 14-pin version of this lock
Note: You can see that the chambers are not positioned in a straight line
Shear line in back of Sliding front with correct key
Shear line in back of Sliding front with false key
Han Fey, July 2006, Drumm Geminy Shield 4
You can see that the Sliding front is effectively blocked against sliding. In the picture below, you can
see a blank for a 5 key pin and two 14-pin keys.
A blank and two 14 pin keys
Note: The key blank is shown staged, awaiting the insertion of key pins
Something about the key pins
There are 3 different heights possible for the outer diameter pins and 5 different heights for the inner
pins. This adds up to 10 different key pins. You can find the coding and length of these pins in the
table below.
Pin number Height outer diameter [mm] Height inner diameter*
11 1 1
12 1 2
13 1 3
14 1 4
21 2 1
22 2 2
23 2 3
31 3 1
32 3 2
33 3 3
* referenced is the outer diameter, the tip is x mm higher as the outer diameter.
Some key pins in detail (code 11,13,14,21,22,32,31)
If you have a close look at some of these key pins, you can see that there are pins with three different
heights. This is part of their new production process. The keys are made by pressing the key pins into
the holes in the frying pan key. Because the outer diameter, where the press pushes on, can have
three differing heights, the manufacturer developed a technique to produce these keys more
efficiently. He made an extra outer diameter (see arrow). When the key pins are pressed into the frying
pan key, this special outer diameter ledge is used. This “extra” diameter provides for a means of
indexing the depth of each individual pin’s penetration.
Han Fey, July 2006, Drumm Geminy Shield 5
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