Questions about safe deposit boxes.

[Drifty Flintlock]

Well, I signed up for a safe deposit box at my bank recently, and just looking at the key they gave me got me immediately interested.

http://imgh.us/deposit.jpg (hi res warning)

I did some looking on Google but there's surprisingly little information about deposit box locks or keys. The only thing I really found was a video of a Diebold 175-70 being picked on Youtube. I think the box at my bank is either that or from the same family, but there's still some stuff I'm curious about. I'm not so much looking for information on how to pick them. I mean, that would be interesting, but I doubt I'll ever have the chance and it looks like you need special tools anyway. I just want to know some things about the internals.

1.) The whole body of the key is pretty unusual compared to the normal stuff I've seen. What's that lone notch toward the back of the key all about?
2.) The business end is quite interesting as well. The bitting is very small and close together. The cuts are square and sharp compared to most keys I've seen. Why doesn't it get hung up in the lock? Is it even a normal pin or wafer lock, or is it something weird and exotic?
3.) What's that little protrusion at the very tip? Does it actually do anything?
4.) How does it require two keys to open the deposit box, in mechanical terms? My best guess was that one lock turns a bolt on the left of the box and the other turns a bolt on the right, but I'm far from sure about that.
5.) Anything else interesting going on in there?

PS - I know there's a certain amount of risk is posting a picture of a key, but given that nobody knows where I bank or has enough personal information to impersonate me to the tellers, I can live with it.

[billdeserthills]

I would say that lone notch sounds like the Throat Cut. Without that cut the keyway will not turn

Your safe deposit box has a Dual Custody Lever Lock on it, which is very different from a pin tumbler lock

The protrusion at the tip is actually centering the key inside the lock so it rests in the correct place to press against the lever tumblers

The lock is usually built in a way so two fences are mounted on one movable plate that the bolt is connected to. When the lever tumblers are correctly lined up, a gate is formed that the fence will be able to slide into. The Guard key which is retained by the bank will cause the gate in each of the tumblers on their side of the lock to line up in front of the fence. Your key will cause the gates in the levers on your side of the lock to line up for the second fence and also shove the two fences over, which retracts the bolt and allows the door to open. I wish I had a picture or a drawing but I suspect we are very close to advanced territory now anyway.

I found a picture that shows the inside of a lever lock your safe deposit lock likely has similar parts in it's interior, with the addition on a moveable keyhole which neccesitates the throat cut. Also what these guys call "a Stump" I called a Fence
http://lockwiki.com/index.php/Lever

[jtucek]

2.) The business end is quite interesting as well. The bitting is very small and close together. The cuts are square and sharp compared to most keys I've seen. Why doesn't it get hung up in the lock? Is it even a normal pin or wafer lock, or is it something weird and exotic?

Bill's already given you most of an answer, but to repeat, it's a lever lock. It is an older technology compared to your standard pin tumbler lock; modern-type"Yale" pin tumbler locks date from 1851, while modern-style lever locks date from 1778.

In North America, you basically only see lever locks on safe deposit boxes and safes. I've never even seen a decent lever lock offered for sale in the US for a deadbolt or padlock (I have seen really crappy ones). In the UK, lever locks are still used, mostly due to insurance regulations dating from when lever locks were the only secure option. In other places in the world they are still sometimes in common use; for instance, in Taiwan people often have lever locks on their apartment doors in addition to a more "normal" pin-tumbler lock.

[Drifty Flintlock]

Ahh, interesting. I was vaguely aware of the existence of lever locks, but I had never actually seen one before. I'll start doing some further research on them. Thanks guys.

[billdeserthills]

The last, most recent use of lever locks in the US was for rural post office boxes located outside the usps. I still have a bunch of old, new stock of them. They are found mostly now on antique furniture
and look like a warded lock using a bit or barrel key. A few keys will open almost all the warded antique locks, but the lever locks from that era can be difficult to impossible for me to open, or impression a key to. I do seem to have some success at impressioning keys to most of the lever locks I have in my collection tho I wouldn't have a try at a safe deposit lock. I have opened a few at work that were missing the keys, but I just destroy the thing & replace it with a new one. I know in the long ago things were different. I had an old locksmith friend who used to drill for the view hole in the front of the lock. Almost every lever lock has a view hole drilled in the side where you can view the fence & the levers. Then he could cut a key, or more easily pick the lock. Afterward of course he would repair the door of the box. I better stop here so we don't get put into advanced...

[2octops]

Safe deposit box locks are typically dual key lever locks. Some have 2 independent sets of levers, one that the banks key operates and another set that the renters key operates and retracts the bolt. Some have 1 set of levers that the bank key operates part of them and the renters key operates the others. Neither is better than the other, simply different designs from different manufacturers.

The cut towards the bow of the key is a throat cut. The nose of the lock (the round part that you can see) has a lip that sits inside the throat cut in order for the key to turn. If you look closely at the nose, you will notice a notch in line with the keyway. This is so that you can insert the key.

Inside the lock is a stack of levers that each of the square cuts in the key line up with. If the cuts in the key are correct, it will raise the levers all at the same time to line up a notch in each lever so that the fence post of the locking bolt can retract into the levers.

The banks key lines up the levers for one fence on the bolt, but can not retract the bolt. The renters key then lines up the other fence and retracts the bolt as the key is turned. The banks key must be turned before the renters key can be turned to retract the bolt.

The small tip of the key simply slips into a notch in the back of the lock so that the key properly lines up with the levers.

These are elementary locks that are easily defeated with the correct tools. They have been in use for many, many years and work very well for their intended use. They are not high security locks and honestly don't need to be. The actual security of the safe deposit boxes comes more from the banks policies and procedures. Typically, there are only a couple of people in the bank that has access to their key. Without their key, the renters key will not work alone. Banks typically also will have their employee sign you in to access your box, then go inside the vault with you and insert their key into the lock and turn it, then allow you to use your renters key to physically unlock the box. They will typically allow you to remove your bin from the nest, then carry it out to another private location so that you can open the bin alone and get out or put in whatever you want. They also do not normally allow more than one customer inside the vault at a time.

The real physical security is the actual vault that the nests of safe deposit boxes are stored inside of. They are extremely well engineered and built with a time lock on the door so that it can only be opened during normal banking hours.

Here's a pic of a typical sd lock with the cover removed that might be helpful explaining how this works

[jtucek]

These are elementary locks that are easily defeated with the correct tools. They have been in use for many, many years and work very well for their intended use. They are not high security locks and honestly don't need to be. The actual security of the safe deposit boxes comes more from the banks policies and procedures.

Not speaking about any particular lever lock, but it really isn't fair to brand them all as "elementary". I've seen some really crap (not even elementary.. preschool?) lever locks, but there are reasonably high security lever locks available outside of North America. A standard quality lever lock is likely more secure than a standard quality pin-tumbler, simply because the tools & training needed to pick a lever lock are not as common compared to pin-tumbler. OTOH, in North America, you're not likely to find a "standard quality" lever lock, but instead something rather worse. Outside of safe-deposit boxes (which do rely on policy and procedure for a lot of their security, but still typically have good locks regardless) I've never seen anything better than a 3-lever lock (probably uncurtained and without overlift protection) in the US. To repeat myself, 7 or even 9-lever locks are not uncommon in Taiwan, and 5-lever locks are considered "standard" in the UK.

Lever locks were *the* high-security lock technology for a long time. Lately they've been ignored. The current best pin-tumbler (or disc detainer, or magnetic) locks are better than the best lever locks, but I'd argue that until pin-in-pin like Mul-T-Lock, rotating pin like Medeco, or some of the better disc-detainer locks from Abloy were introduced (all in the late 60's-early 70's), the best lever locks were the top of the line in key-based locks. The last 50 years has seen them fall behind, but I'd still trust a good one more than your run-of-the-mill Kwikset.

[2octops]

Yes I mean they are elementary. I agree that there are many lever locks being made today that are excellent locks that are extremely difficult to pick or bypass. Safe deposit locks are not one of them.

We have serviced a lot of banks over the years and dealt with many, many different manufacturers sd locks. There are very few that take longer than 1 minute to defeat and swing the door open as long as you have the bank key. Even without the banks key, it only adds another minute to open. Sure this is a destructive method on many, but the locks are extremely inexpensive to replace and in the field time is money.

Diebolds pick quickly with the correct tool, Moslers, Miles Osborne and S&G almost fall open if you look at them hard enough. Lefebure can be a pain without the proper tool and knowledge of how they work.