After turning the key and dialing the correct combination, the unlocking handle on the basement safe refused to move. Applying the dictum “If brute force isn’t working, you’re not using enough of it”, we eventually persuaded the handle downward and the door swung open. Before applying the dictum “If it doesn’t move and should, use WD-40 [*]”, I had to remove the trim cover from the interior side of the door to gain access to the lockwork.
Start by pressing the two latches inside the small circular holes in the hinge side of the trim cover:
Pull the trim over the slightly chamfered bolts, taking advantage of the fact the bottom pulls out more easily than the top, then pry it upward off the latch in the middle of the top:
The latches along the other side yield when you bend the trim sufficiently far from the door while applying the Designated Prydriver near the faint mold markings visible around the edge:
With the trim removed, you can see fancier safes in this line have two additional bolts engaging the top and bottom of the door frame. The rectangular block on the bottom of the hinge side might be for the batteries required by the spendy electronic lock version.
The problem turned out to be a lack of lubrication in the door-closed interlock that prevents you from relocking the bolts and wrecking the mechanism when you try to close the door with the bolts extended:
A dab of silicone lube on all those sliding interfaces restored the interlock’s good humor.
The bolts had always rubbed just a bit on the trim cover, so I ovalized the offending side of the holes with an Xacto knife.
Slamming the trim firmly back on the door reset the latches, cycling the lockwork resynchronized the interlock, and the safe once again works just like it should.
[*] WD-40 is not the appropriate lube for the lockwork inside a safe, but the dictum aims you in the right direction.
The Smell of Molten Projects in the Morning 
The Sentry safes don’t have a great reputation for reliability. The solenoid that disengages the lock on my electronic version failed after a few months, preventing the safe from unlocking. But a wack with a hammer in just the right spot will get it to open. Some security!
You need to be careful about applying too much force to the handle when trying to open the door, otherwise the plastic gear will strip and then you’ve got a dead safe. Fortunately (?), you can cut them open with a circular saw in less than 2 minutes. https://www.youtube.com/watch?v=2guvwQvElA8
My, that was straightforward. I have a saw exactly like that one and wondered about the depth of cut; turns out one layer of sheet metal is all it takes.
I had no illusions about overall security, because (as with PC security) anybody with physical access has “root” access. The most likely threat is having the place burn down, not encountering a burglar with enough time / skill / tools to take the thing apart.
So far, so good, on both counts!
Your pictures remind me of an only slightly related story.
Many years ago I was working for a locksmith in Arizona and we did a fair amount of work for the local police and sheriff’s departments. I was called out to open a “safe” in the home of an accused drug dealer. What I found was a fire-resistant document container much like the one in your pictures. I could have popped it with a crowbar, but I wanted to make the container penetration look good so I drilled into the lock body and dialed it open. I let the LEOs open the container and found out from one of them later that there was over seventy thousand dollars in cash inside it.
I remember thinking–you got seventy grand to stash away, and you couldn’t afford to spend a couple of hundred on a real currency rated safe to store it in?
If you’d found a real safe, could you have justified explosives? [evil grin]
No, but I did once get to use a rented thermal lance on a vault door, and that was pretty close. Scariest piece of hardware I’ve even handled.
Boggle …
Puckers me up just thinking about it.