Well, I collect US gold coins, and study them. (numismatics)
The best area I'm at in those is counterfeit detection. That's where my name came from, spark erosion is a type of counterfeit coin process fakes use.
I'm also a magician (I do magic with sponge balls and coins)
Here's a picture of the coin:
NGC is the grading service. These are professions who, for a fee, will take your coin and grade it (Grades range from PO-1 (Poor-1) to MS70, a near perfect coin with no flaws). The condition of the coin determines its price, among other factors. NGC, PCGS, and ANACS are the 'top three' grading services for coins. They will also authenticate your coins (especially important in gold coinage)
Did you know the US mint once made a 2 cent piece, a $2.50 dollar coin, and 3 cent silver and nickel piece?
CAC is an independent third party grading service which looks over already graded coins (PCGS or NGC only) and determines if they are 'high end' for the grade. You can either get a green or gold sticker, or no sticker. Say you have a coin excellent for the grade, or "A", and a coin better than average for the grade or solid for the grade, "B" and average or below average "C". CAC would only put the green sticker on "A" and "B" coins, not stickering "C" coins and if the coin is especially undergraded (which is a good thing), it will give the gold sticker. The green and gold stickers supposedly bring premiums.
In 1933 president Theodore Roosevelt called in the public to turn in all their gold coinage, making it illegal to possess gold coins that aren't rare or have high numismatic value. At the time many americans were loyal to it and turned in all their gold coins...this also ended the gold standard. (You used to be able to turn in silver or gold certificates, paper money, for gold or silver).
Much gold was melted, making otherwise common date coins relatively rare. As the dies to strike the coins wear out, the luster on the coins change. There are terms such as EDS and LDS which stands for 'early die state', 'late die state', describing the condition of the dies. Dies for striking coins are highly polished, leaving what are called polishing lines on the finished coin, these are often swirly in the protected areas of the coins. This paticular coin I have here is semi PL or semi prooflike, that is, its partially reflective while it still has some cartwheel luster.
Die wear's characteristics on luster goes as follows:
PL = new die w/o evidence of metal flow
semi PL = new die beginning to wear
frosty = die w/notable flow lines, carthweel effect
satin = die with little evidence of metal flow (LDS I think)
flat = die w/o flow lines or worn die
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I also do magic, here's some of my stuff I do:
Here's winged silver by david roth.
YouTube - The Stuff
Here's the one with my boring vocals:
YouTube - Video 20
My mastery (finally) of the four coin roll down flourish:
YouTube - Roll Down
David
stone "Bridal journey"
YouTube - Video 12
Few others:
Slydini sponge vanish with purse frame
YouTube - SohCahToa.wmv
Flourish with rings, the insanity ladder from de'vo:
YouTube - Created
All 102 videos are on
YouTube - Fishsticks911's Channel 
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