How I opened the safe

The first thing I tried was to follow the instructions given in "Safecracking for the computer scientist". If you are not an expert, you will have to read some parts of it if you want to understand the following in detail.

Essentially there should only one place where you feel a change in resistance when turning the dial, it is called the gate. The gate will be found at the same location each revolution. For this make and model of the combination lock (Sargent & Greenleaf, group 2, three wheel lock) it should be somewhere between the numbers 95 and 15. For a combination lock of this type and if it is in good condition it should be easy to found by feel (not so much sound). The lever nose drops into the gate each turn. If all the other wheels (three in this case) are aligned correctly the lever nose will drop into the gate all the way and enable the unlocking mechanism. The method of manipulating the combination lock (finding out the correct combination) relies on small imperfections of the wheels. Essentially one systematically dials in different combinations and measures how deep the lever nose dropped into the gate. This is done by finding the left and right contact points between the lever nose and the gate (they can be felt). The results are graphed and ideally one number of the combination can be read of that graph. Then a few experiments can indicate which place the number has in the sequence of the combination. The experiment is then repeated in the same fashion, only by presetting that found number while changing the others. If one is able to detect the locations of the left and right contact points accurately and repeatably one should be able to find the correct combination in less than an hour.

Well all that sounds reasonable straight forward, only that my dial was not turning easily and randomly sticking. I was able to find the gate and even get a reasonable idea where the left and right contact points were but a few experiments showed that my measurements were not reliably repeatable. It was just to difficult to turn the deal smoothly and feel the subtle change in resistance.

My next attempt was to apply some WD-40 to the combination lock and that improved things greatly. The dial was now turning smoothly and the change in resistance stood out very well. So I made some safe cracking graph paper and made a few runs of filling them in:

One has to look for where the left and right contact points are the closest to each other. I found some areas of interest and one place around numbers 70 to 75 were there was a big jump in the size (the nose lever is held higher above the gate), but I could not reproduce the areas of interest by closer investigation. Generally I found it difficult to determine the contact points to the required accuracy.

During my time of dialling in different combinations I noticed marks on the knob of the dial.

I had noticed them before, there were two sets of different marks (lines and round holes) with four marks for each of the sets. A safe expert on All Experts had already suggested to me to try these marked numbers. I discounted them since I was sure I only needed three numbers in my combination and it is very hard to tell to which exact number each mark belongs. I found however that the set of round marks had one mark on zero. I discounted the zero mark and rounded the remaining three marks to their closest multiple of 5 numbers. This gave me three numbers to work with for which there are nine different orders of dialling them in. I wrote all nine sequences down and started dialling them in systematically (see this entry on how to correctly dial in a combination). The lever nose clicked very audible into the gate after dialling in my third combination. I turned the handle and the safe opened revealing that is was stuffed full with things.

I will write more about the content and the safe soon. I want to have a look at the combination lock from the inside (see what happens between the numbers of 70 and 75) and maybe even set my own combination.

The safe is open!!!

I opened the safe last night. I don't have much time at the moment, therefore will post details soon.

I opened the safe using the correct combination. Some combinations were marked on the dial and one of them worked.

I heard the lock engage and using the handle pulled back the bolts. To my surprise the safe was completely filled up with stuff:

Most of the left compartment is filled up with silver cutlery. There are necklaces (nothing special I think), photos, documents and other bits and bobs.

I will write more about the contents and the other opening approaches I used later.

Some expert input

I found this site All Experts where experts offer help for free. There is a section for Antique Safes where Andy has great knowledge and advice.

According to him my new safe is from the late 1940s to the mid 1950s. The lock is a HHM three wheel lock, capable of 1,000,000 possible combinations.

A combination, for example 60-25-50, is dialled in by:

4 times left to the first number (60)
3 times right to the second number (25)
2 times left to the third number, (50)
1 time right, slowly until the dial stops (around 95).


Further I found this howto which explains the locking mechanism very well and has an animation of it which clarifies the details. It describes a method of manipulating the lock to obtain the combination, but this section is lacking detail and is incomplete I found.

The missing bits and much more can be found here in "Safecracking for the computer scientist". It gives a detailed account of the inner workings of the combination lock and how to find out the combination.

Closer inspection of the safe

The safe is 50cm wide, 70cm high and 51cm deep. At the top left it says in golden letters:

Herring Hall Marvin Safe Co.
Hamilton Ohio

At the bottom of the door there is a sticker with the same information:

Underneath that there is a plaque that says:

Underwriters Laboratories, Inc
Inspected
Locking Device
Group 1 No 114275

On the top hinge is a serial number:

15542

The combination dial has 100 positions, the knob shows HHM (for the make).

Right from the dial are two drill holes. Drilling into the locking mechanism is a common way of opening a safe. The combination disks can be aligned visually or the opening triggered manually. For this reason some safes have cobalt plates embedded near the lock which is very difficult to drill and requires specialised equipment.

The right hole is only shallow. The left one is about 40mm deep but does not penetrate the locking mechanism. I don't think these holes were successfully used to open the safe.

In the base of the safe a section has been cut out. The outer hull has been cut away, the insulation (concrete) has been removed. Another metal layer beyond that has been cut out and bend to the side. Behind that there is a sheet of metal, which in my opinion, has been put there from the inside to close the hole.

I think somebody got into the safe this way and probably managed to unlock the safe through this hole from the inside. This means if there were any drawers or compartments in there, these would have been damaged in the process. Of course I don't know when that happened, but I don't think I will find great treasures (maybe a business card from a locksmith).
This is the safes weakest point at the moment. The metal sheet could easily be cut away.

The safe arrives

Today the safe was delivered by the seller. It was easier to move than I expected, due to wheels that allow it been pushed sideways. I estimate the weight top be somewhere between 100 and 200kg. I could easily manoeuvre it into the basement.

My first impression is that it looks better than on the pictures. For some reasons the safes surface appears rusty on the photos.


I am publishing more photos of the safe here:
Safe Photos

The seller told me that he bought the safe in an household auction after the owner died in a car accident. The drill marks next to the dial and the cut marks in the base were already there when he acquired the safe.

The make of the safe as stated on it is:
Herring Hall Marvin Safe Co Hamilton Ohio

How I bought the safe

I bought this save on a New Zealand internet auction site beginning of this week:

Safe auction

The seller indicates that the combination to open the safe and the content of the safe are unknown. Further it is clear from the questions and answers in the auction that multiple attempts have been made to open the safe, including drilling and cutting into the base. Wether any of these attempts were successful is unknown.