Collectibles i.e American Gold Eagles or American Silver Eagles are taxed at a different rate, under the Capital Gains Tax.
Now, when dealing with Coins and Boullion, most people never declare they have them in posession, because you could hypothetically hide them very easy, and play dumb. Although, if you do go through the process of declaring them, I don't know why you would... The Tax Break down is something like this:
Short-term capital gains (STCG) One year or less holding time = Ordinary income tax rates up to 35%
Long-term capital gains (LTCG) More than one year holding time = 5% for taxpayers in the 10% and 15% tax brackets (zero percent starting in 2008) 15% for taxpayers in the 25%, 28%, 33%, and 35% tax brackets
Collectibles One year or less holding time*= STCG tax rates up to 35%
Collectibles More than one year holding time = 28%
As a person who thinks like you and also has some Silver, Gold, and Paladium Coins/Bars/Boullion my best bet would be, don't draw so much attention to yourself. If you want to avoid having to pay the 28-35% tax rate on these things, make smaller transactions, or break up your transaction into chunks, so it doesn't look so large.
Either way, avoid letting Big Brother know that your dealing goods/services for gold. They don't like that.