You need to get some books on coins, if your gonna do any serious coin collecting,not just the common redbook either.The knowledge you will gain from them will pay for the books as well as save you money in the long run.The 1879s mint Morgan you refer to is a common date with many fine examples to be had, however,it has two reverse designs and one of them is worth quite a bit more than the other in the higher grades.I'm talking about a 1000 dollar coin versus a 40-50 dollar coin of the same grade depending on the reverse design.It's referred to as the second and third reverse design.Or as the "flat breast" and "round breast" variety.The second reverse which is more rare thus more expensive is the variety where the eagles breast is dished or concave.On the third reverse the eagle breast design is rounded or convex.As far as the price goes,i'm talking about very high grade coins of ms 64 or better,professionally graded of course.Anyway,good luck at the auction,I hope you find a rare one. ps-One more thing,be aware that if a coin has been cleaned it usually lowers the value unless it has been done by a proffesional.