Pro Plumber

I have recently stumbled upon a hidden floor safe in my home. Although it would be reasonable to assume that this discovery would be excessively exciting for someone of my disposition and this group, unfortunately, the excitement was fleeting due to the safe's apparent reluctance to open. I possess the key, which appears to have deteriorated over time, and the safe itself seems to be an antique model from a bygone era, characterized by rust, grime, and an air of intransigence. Before taking drastic action, I would appreciate any guidance from individuals who have experience with restoring old mechanisms to working order. I have already attempted to use WD40, which made the safe extremely shiny but had no other impact. Can anyone recommend suitable lubricants, gentle tapping techniques, or a preferred sequence of patient manipulations? Alternatively, is there a particularly informative YouTube tutorial that I should be aware of? Any advice would be gratefully received. My ambition is modest: to open the safe without causing damage to it or my own resolve. Female, 38, Wales, shoe size inexplicably increased from a 7 to an 8. I hope the safe contains bananas.

Found in the wild. Unable to determine its purpose. Possibly a sump pump, still unusual.