This is based on triple+ hearsay, however presented on a cautionary
basis. When OdySea closed a team of auditors descended on premises.
Another store said they were IRS agents looking for records of those
who bought gold coins and resold them on ebay. Supposedly this store
said the IRS treats the sale as income.
I doubt IRS agents as opposed to Treasry agents would look into a tax
matter. Furthermore it could be argued that the sale of coins should be
netted against gambling losses. Consult your own tax advisor for proper
treatment.
However I would assume a taxing authority may be aware of gold coin
transactions, so I would tell your tax preparer and at least disclose
transactions and tax treatment used in a footnote to your return to
possibly avoid possible penalties, etc.
David