Safe
2 of the 7 encyclopedias on this shelf carry an entry for Safe. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a receptacle, usually of iron or steel, for the safe keeping of money, jewelry, and other valuables. The safe is the lineal descendant of the old-time strong box or oaken chest. As late as 1700 even royalty had no better means of keeping valuable documents and precious wares than in wooden chests, strengthened with rawhide, or with bands of metal. The next stage was the building of very heavy chests so completely covered with metal that they would stand heat in a fire for two or three hours. The modern safe is of two kinds, the steel vault which is built into the masonry of buildings at the time of their construction, and the movable steel safe. The latter is built of double steel walls several inches apart. The space between the inner and outer plate is filled with some non-combustible, non-conducting material, as plaster of paris, asbestos, fire clay , alum, mica, or chalk. The lock has received particular attention. Several burglar-proof locks have been invented, but each in turn has been abandoned for a lock of greater security. The more expert burglars become, the more ingenuity is shown by safe builders. There are probably a few locksmiths able to open any safe constructed, but, generally speaking, a modern safe defies the utmost skill of the burglar. The time lock is opened by clockwork at a given hour. Even the owner cannot open it at any other time. The usual method employed in "cracking" a safe is that of pouring nitroglycerine into the crevices around the door and exploding it by means of a fuse. In the case of expensive, massive safes, the door fits so closely that it is impossible to introduce an explosive. In that case, the burglar aims to drill a hole and insert a stick of dynamite. Train robbers resort usually to this method in getting at the contents of an express messenger's safe. A burglar-proof safe costs all the way from $20 to as many thousands, according to size, material, and workmanship. The vault of the Carnegie Safe Deposit Company, of New York , cost half a million dollars. It is protected by plates of steel armor, proof against the heaviest guns of the American navy. It is designed for the safe keeping of bonds, stocks, mortgages, wills, and other valuable documents. It has been nicknamed the pocket-book of Wall Street . The safe of the National City Bank, also on Wall Street, is another expensive vault. Four hundred tons of steel and seventy-five tons of fireproofing cement were employed in its construction. The doors are eight feet thick. The very hinges weigh two tons apiece. Should a burglar attempt to enter out of hours he would be scalded to death by jets of boiling hot steam admitted through a series of brass tubes connected with a steam boiler. It is hardly worth while to close the doors of the vault, for all around the whole structure are the brass nozzles, which, by the touch of a button anywhere in the building, and in several places outside of it, would render the vicinity of the vault a cauldron of death. The total cost of this remarkable defense against thieves was $250,000. The safe industry of the United States is in the hands principally of ten leading corporations. They have a capital of about $6,000,000, employ 5,000 or 6,000 workmen, and turn out about $12,000,000 worth of vaults and safes a year. See Lock
Collier's New Encyclopedia (1921)
a receptacle for valuables, of iron or steel, or both combined. A safe to answer all requirements should be fire, explosive, acid, drill, and wedge proof. A fireproof safe need only be so constructed that, though exposed to the intense heat of a conflagration, its inner recesses remain at a sufficiently low temperature to prevent combustion of the contents. A burglar-proof safe needs many other safeguards, and the history of safe-making is mainly a record of struggles between the safe manufacturer and the burglar; the result is that safes can now be obtained which are all but impregnable. The safe consists of an outer and an inner wall, the space between being filled material such_as with some fire-proof asbestos, silicate cotton, gypsum, etc. The outside casting, which may be single or compound, naturally receives the greatest attention, and various are the devices of manufacturers to render it sufficiently hard and solid to resist the finely tempered drills of the burglar. To prevent wrenching, the door is secured by bolts slots moving straight or diagonally into on one or on all sides. These bolts are moved by the door handle, and the lock key fixes them in their positions. The first great improvements in locks, as applied to safes, are due to Chubb of London; but numerous patents, mostly of American origin, have been introduced. Of these the keyless permutation locks deserve particular mention, as they obviate the danger which arises from lost or false keys. Such locks allow of opening only after an indicator has been moved ed in accordance with a certain combination of numbers arranged before closing the safe. Some safe locks are so constructed that to be freed they require different keys on different days, some can only be opened at a certain hour, this being fixed on before the door is closed; while others again require two or more keys in charge of different persons; in fact, the arrangements contrived to render the plundering of safes next to impossible are too numerous even to mention. The connection of safes with electric alarms in a variety of ways forms another safeguard.