There is a danger of reproduction coins being innocently bought by amateur coin collectors as the real thing.  While such coins bear the letter C - copy or R - reproduction, unscrupulous dealers are often able to remove these telltale signs and adequately disguise them by "damaging" them slightly.  Like the fake £1.00 coins (made of lead and sprayed gold) that came onto the market when they first appeared, the discerning collector should keep a wary eye on what would appear to be too good to be true at a much reduced price.

There, Chris.  Exactly what you had suggested, but in one-fifth the number of words, and no yelling - use of capital letters throughout.  In other words, get to the point in the first sentance! 

As an aside, the same could be said about collecting old medals.  You've got to keep your eyes open and common sense engaged.  If you see a bloke selling an Iron Cross on a coins and medals stall at Victoria Station or Portobello Road for £30.00, then OBVIOUSLY common sense should prevail!