It never ceases to amaze me when I see a so-so quality coin with a high MS rating given out by a 3rd party grading service.  While I cannot name names due to legal reasons, I can say that if the coin is not graded by PCGS, NGC, ANACS or ICG...DO NOT TOUCH IT!  You will find that for instance a MS67 Morgan Dollar graded by another grading service, will really fetch you an MS60 if you are lucky by the four grading services I have listed.  Sellers can of course get away with saying the coin is "certified" and you will also see the explanation, "Grading is subjective" in their definition of the coin, but do not be fooled!  And of course, never assume a grade when the coins you are bidding on are stapled in a cardboard square but the seller grades the coin himself.  Be smart out there!