Lasering Gold

Dahlonega

Been hearing about this with increasing frequency for past few years. Anyone know the details on exactly how it's done?
What type/kind of laser...wattage?
Only for clean proof coins or is crusty, circulated gold amenable?
Anyone have a before and after picture of a lasered gold coin?
Is it detectable by an educated numusmatist? If so how, what do we look for?
I've heard a lot of second and third hand rumors anyone know the 'real skinny'?
Detectable by major grading services?

HJP

Hi Dahlonaga,

There are several different laser irradiation techniques that may be used to alter a coins surface. I have been told that a CO2 laser with a few hundred watts of power and various types of focusing lenses is what is used. My understanding is that depending on the "defect" to be repaired that the laser will be operated in a pulsed mode while rastering the beam and gradually adjusting the power level until the metal begins to flow. I have seen laser treated proof gold were the laser reflowed the surface to remove hairlines. It is not easy to detect this when the lasing is done by an expert, however there are a few specific characteristics that can be used to diagnose the coin, such as the flow pattern and grain structure of the surface (this takes fairly high magnification to see in most cases), as compared to the surrounding area.

I believe the grading services have now had some training in how to look for laser alteration, so I hope this "doctoring" technique will become less & less prevalent. The real problem I see for the grading companies, is what is going to happen when a coin in thier holder has been determined to have been altered, as many of these coins run in the 5 and 6 figures?

Hope that helps,
HJP