How do you sell unmarked gold ingots? Plus, the value isn’t just the gold itself, but the antiquity. It’s not that hard to sell an antiquity one piece at a time.
Sell one a month and you’re doing well. Keep your job, use the money to save and save. Retire in ten years or so and no one’s the wiser. Too much greed ruins the deed.
Gold is testable, probably cost you something, but they sell gold dust all the time to an assayer. I agree on the antiquity value, but once discovered, you'd have little chance of keeping it.