I found a locked safe hidden at the back of a closet in my new house

Safes all the way down?


Only until it gets to the turtles.


It didn’t go so well for the contents (or the safe) the last time they tried opening a safe. Water damage plus explosive damage plus smoke in a new house doesn’t sound like such a great idea.


You’re absolutely right, I had that backwards. I reread that section of Surely You’re Joking, Mr. Feynman last night, and I had remembered it wrong. On re-reading, I also saw that Feynman found the hint about looking for nearby notes jotted down by reading books about safecracking, but he’d come up with his own set of tricks for figuring out the last digit or two on various types of locks, especially when he could feel the motion of the locks when they were already open, and using that to shorten the number of combinations to try.

But I had remembered correctly how both he and the locksmith each thought the other must be a brilliant safecracker, and it turned out all they had was a bunch of different tricks they’d each figured out for themselves. Fun book.


Make sure you try 25-0-25 and 50-25-50.


Clearly, you can never open it. The contents can’t be worth more than the mystery.


I remember the film. Yes, there was no leak plugging in the film, but they were filling the safe from the sprinkler system, so they could have just left the water running. The underwater explosion and collapse looked real, and I thought at the time ‘that ought to work’. And they were rescuing a sceptre in a piano leg, and it would still be worth something if it got bashed about a bit. It’s nice to see films can get something mostly right, sometimes.

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You might have missed the part where cutting the hole destroyed everything in the safe…

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Of course, since even found windfalls are subject to income tax, the safe is guaranteed to be cough"empty"cough…


Some safes are designed to permanently lock themselves, or otherwise mess with you when drilled or breached in certain ways. As much as that seems to be a modern thing, I’ve seem some pretty old safes with features of that sort. At flea-markets, in antique shops, on the teevees, and assorted other media. Along with crazy booby traped safes, safes with fake doors and false bottoms etc. Vintage security equipment is varied and delightfully weird. I would really doubt this would be that sort of safe though. From the picture it looks to be a pretty bog standard sort of American home/business safe. My concern was more with amateur drilling causing unintended damage. Or what sort of reduction in value might come with that little hole. I would imagine that to collectors a safe that’s been professionally drilled is worth less than a safe that’s in pristine working order.


Thought. Could ultrasound show the insides of the door?

Tricky. Most of the sound would be reflected by the first inside surface. You have to preserve energy with a continuous sound wave, energy and momentum with a shockwave. and there is no good way of matching the impedance of metal to air. Fill the safe with any of the low temperature metal alloys such as Woods Metal, and you might get somewhere. But that’s a lot of stuff to carry about.

What about xray backscatter? Or neutron backscatter (probably not as it’d work poorly on ferrous alloys)?

The locks in the document safes at a certain MoD establishment I used to work for had a lead addition to the lock, with deep concentric circles. Apparently this was in case someone asked you to lock up a radioactive source for them, then they taped film to the outside of the lock. I don’t know if anyone had ever done that, but this was supposed to make it very hard. Neutron sources might pick up on the grease in the lock, as they are crankily sensitive to low-Z materials, and an edge coated in grease might show up well. But you would probably have to have the neutron source inside the safe to get a sharp resolution.

If we get strong enough xray source, could we shine through the whole safe and the wall it is mounted on? How strong source would be needed?

The devil is again in the detail. The nice thing about sticking the radioactive source inside the safe is that it minimised the scatter. If you have a big burst of X-rays and you are trying to see through 100 g / cm2, then you are likely to get as much signal back from backscatter from the walls of the building as you will get from X-rays getting through the safe itself. You can correct for this to some extent. The most penetrating radiation you are likely to find would be Cobalt 60 at about 1.2 MeV. Lower energies do not penetrate so well, while higher energies have losses due to electron-positron pair production.

Time-of-flight acoustic tomography might work. But these locks are mostly circular elements on a shaft. You could detect a notch in the circle, but it would be much harder to say which way it was pointing. However, you can move your sound source either side of the shaft, which may give some resolution.

Yay, science!


No, I didn’t. There was other stuff in the safe in the film, and most of that was reduced to slag (see other note about thermic lances) but the object was in gold, and so would still be of value if a bit fused. In the MythBusters version, the safe was mostly empty. Good programme, though.

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Here, this’ll save you time:

“We haven’t even come close to opening the door and already the loot, including my prize scepter, is already mostly destroyed.”

In the film the sceptre is only worth anything as the sceptre itself, not as a chunk of gold. If that was the case they’d just hand him some much-easier-to-procure melted gold of the correct weight and call it a day.


What about filling it with water? Would still not be a perfect impedance match but would be way better than air.

Whoa. Never heard about this. (Thanks!)

Drill a hole, push it in?

A grid of parallel lead plates, acting as a collimator, getting rid of the scatter from other directions?

I thought more about a pulsed power xray tube. Radioactive sources are a bitch to handle.

Maybe a cold cathode pulsed xray tube fed from a Marx generator?

Or use an array of transducers, using one as a source and others as microphones, and scan the pulses through the array?

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What is on the back side of the safe? Another wall, a room, outside wall, John Malkovich’s brain?
Myself, I would try to open it to see if it is serviceable.
I think it would be fun to go online and try each “Safe Cracking Method” listed and film your results.
But as someone who is a Locksport hobbyist, sometimes I buy padlocks at the flea market without keys or combinations and the lock is just no good and broken.


Yeah, but since he bought the contents with the house, surely it would be capital gains tax that applied?

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If there’s only one reason to claim you found nothing, it is to avoid the paperwork.

Because fuck paperwork.


Dunno. Either way: tax.

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That sounds like some gun nut wackadoo conspiracy theory crap right there.

I’d imagine in the majority of home invasions the “bad guys” want to get in and out without having a conversation with the homeowner.


But that’s not what movies tell me! Bad guys always want into the safe room!