Disclaimer: My first Trek story. Standard disclaimers apply. TNG is owned by Paramount, except insofar as it exists in a parallel universe. If you're looking for the Trek stuff, that's in chapters 2 onwards for the most part. Please do not kill me.
The date: November 1996
The man couldn't read the inscription. That didn't matter. He doubted his bosses could, either. That, too, didn't matter. Given the total lack of security, he rather suspected the people who technically owned it didn't realize it was there. Convenient. That meant they wouldn't miss it. The quarter of a million advance, same after, that mattered.
He didn't ask questions, especially ones like "why are you paying half a million for a slab of rock with markings on it", as those tended to deprive people like him of an honest living. Well, he wasn't lying to anyone, so it wasn't dishonest as such… Lifting the rock from the underground fault was simplicity itself. The vault was in a more-or-less intact Bronze Age tunnel that ran under the mansion. He had broken in through an almost intact Roman hypocaust, buried deep in the ground, that had itself run over a section of tunnel that had run close to the boundary of the modern-day property.
From there, it was a simple stroll through the decaying stonework, past all of the surface-level security, to the antechamber and then to the vault itself.
The return journey was equally uneventful. Through the tunnels, a scramble up to the hypocaust, a short crawl through, then a pause until a guard went away. A scramble over the fence and nobody was any the wiser.
Handing over the stone was an altogether briefer experience. The man in the shadows showed the money was all there and accounted for. The thief, in turn, placed the stone on the table before screaming in terror and agony as his life force was ripped from him.
The shadowy man in the shadows smiled. Apparently there would be no charge for the service today.