Hello,  having been a collector for more than 30 years I have aquired a pretty good knowledge of a coins grade. I know how difficult it can be if you have to rely on the sellers grade.. I have studied over 10,000 pics from different grading companies aswell as having a large collection of them in my personal collection.    What you must remember is  most Professional Grading Companies have their own method therefore grading fluctuates immensely... Its nice to think that they are always right , but that is not the case.. I have personaly UNSLABBED over 100 coins and resubmitted them sometimes even to the same company and lo and behold the grade almost always came back different..... So here is my advice... Save as many images of graded coins, from different companies and study them thoroughly until you feel comfortable with the knowledge you have aquired... If you are not sure you can go back to the images and compare them with the coin you are looking at , or seek advice from an Ebay member as myself ... Most members are very nice people who are willing to help the novice and even the advanced collector...Most of all if you are not comfortable with  the grade a seller asigns  DONT BUY IT. or ask questions why ..Remember that a grade is only an OPINION..This will make your experience of buying more pleasurable... Take care and I hope this helps a little ....