Corrosion could be induced by putting the gold in a more oxygen rich environment and perhaps making it a bit moist, but it's unlikely that an authentic corrosion profile could be forged. The paper I was using as a source mentions:

"Despite its chemical stability, gold possesses a rich oxidative electrochemistry resulting in the formation of gold oxide coatings and, in the presence of complexing agents, oxidative dissolution processes. Such electrochemical processes are sensitive to changes in the textural properties of the metal surface, reflecting most minute alterations of
the gold surfaces upon aging."

This indicates that it's not just the corrosion that is important, but rather the corrosion and the fine mini reactions.

For your second question, yes storage conditions change corrosion rates substantially. However, this can be accounted for chemically (acidic soil vs basic soil, wet vs dry, etc). This plays a part in the "presence of complexing agents" quoted earlier.

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As well, the authors used known specimens as calibration standards. Those specimens were in various storage conditions, so can be compared to new specimens found in similar conditions.