Most antique safes were intended to be fire resistant safes — they were filled with concrete or some other material for that purpose. This is what makes the walls so thick and what makes the safes so heavy. But in the “old days” there was no standardized testing program, so it was all just a guess. Some years ago we even found a note from a manufacturer glued to the bottom of a drawer inside a safe. The note said that the fire resistance of safes was an inexact science, and that if this safe ever went through a fire it’s condition should be reported back to the manufacturer to help them gauge effectiveness of their fire insulation.
Two months ago a customer brought in an antique Alpine brand safe. Her house was completely destroyed by fire. Pictures of the burned house showed that the only spot where rubble stood more than 2 feet tall, was the place where the safe rested underneath charred remains. When our technician opened the safe (they rarely work after going through a fire) it was found to be completely full of papers, none of which were burned. It’s impossible to predict, but not all antiques would have held up as well as this Alpine. The woman was thrilled to recover all her documents, and she kept the safe even though it was no longer useable.