While your coin is showing gray, this can be achieved by coating the coin with zinc. There are YouTube videos on how this is done. But a closer View of the surface would probably show an example like this one:

Note on this coin your can see the zinc bumps that were plated over (before they knew what the issue was back then) are still present. Just coated by zinc. You can see see a split that is showing the copper plating. These are faked errors, sold to the un-liery on ebay.
The real examples show smooth fields on the coin:

Not the rough finish on the faked missing copper plating coins.

Note on this coin your can see the zinc bumps that were plated over (before they knew what the issue was back then) are still present. Just coated by zinc. You can see see a split that is showing the copper plating. These are faked errors, sold to the un-liery on ebay.
The real examples show smooth fields on the coin:

Not the rough finish on the faked missing copper plating coins.




















