What if you use some tool and hammer to overstamp the serial numbers. Like scribbling over it. Then grind it down. Or if it is in a place that can be heated and cooled... like annealing... where any loss in strength from the operation, were it to happen, wouldn't be an issue. Would that change the underlying crystal structure significantly. I'm sure it would affect it some, but would it be enough to allow the crystal structure to 'reset' and erase the original stamp marks?