What an old treasure we've found in a small local cinema: a very very old battery backup system consisting of perhaps NiFe (or NiCd or lead-acid?) cells and wall charger (switch box). Cinema's technical equipment (projector and the emergency lights) was based on DC safe voltage so it could be easily backed up from batteries.

In the old days, they knew how important is to back up the key infrastructure. But nowadays, you won't find such a thing in the modern high tech 3D cinemas, letting alone the sewage plants, or many of the gas stations...