Chase bankers made a stunning discovery — a gun and empty clips in a safe-deposit box, where it had sat unclaimed for 33 years.

The .380-caliber Beretta had been left at the 1 Chase Plaza branch by former stock trader David Rosenzweig, 56.

The businessman — who now lives in Nantucket — had forgotten about it.

“I assumed [they had opened the box] . . . 30 years ago because I had forgotten to pay,” he said.