What This Coin Looks Like (Obverse, Reverse, Mint Mark Location, Special Features, etc.): There were numerous varieties of the 1880 CC Morgan Silver Dollar. The varieties can be divided up between the "Reverse of 1878" and "Reverse of 1879" type - featuring different designs on the reverse of the coin.
The reverse of 1878 is actually the earlier design which can be identified by noticing how the eagle had an unnaturally flat or concave breast. The easiest way to identify this variety is to look at the arrow feathers on the arrows that the eagle is holding in it's claw. The top feather is straight and parallel along with the rest of the arrows.
The later reverse of 1879 variety was changed to give the eagle a rounder and more convex breast appearance that looked more natural. Again the easiest way to identify the reverse of 1879 is to also look at the arrow feathers. Unlike the reverse of 1878 - the reverse of 1879 features a prominently slanted top feather on the arrow. The difference between the Reverse of 1878 vs Reverse of 1879 Morgan Silver Dollar is depicted above in the example comparison image with the features depicted by the arrows.
Reverse of 1878 had two major varieties: 1880/79 CC overdate and the 1880 8/7 CC overdate. The 1880/79 variety featured an 80 struck over a 79 which resulted in the underlying "7" being clearly visible within both the top and bottom portions of the "8" - and the underlying "9" clearly visible within the "0" as well. The 1880 8/7 however did not have an underlying "9" visible within the "0" - and the underlying "7" is barely visible. The bottom of the underlying "7" can actually be seen as a small bar or dash just below the "8" - and a very subtle piece of the "7" can be seen within the bottom portion of the "8". The difference between the 1880/79 vs 1880 8/7 CC Morgan dollar varieties is depicted below in the example image of the coins:
Reverse of 1879 had three major varieties: 1880 "8/7 (normal date)" - 1880 "8 Over High 7" - and 1880 "8 Over Low 7". Both the high and low 7 feature the underlying "7" clearly visible both within the top and bottom portions of the "8" - and a small bar or dash is seen below the "8". The high "7" is positioned higher and the dash under the "8" is closer to the "8". Whereas the low "7" is positioned lower and the dash under the "8" is further away from the "8" - both varieties are fairly easy to identify.
The 1880 8/7 "normal date" variety does feature an 8 over 7 overdate (All 1880-CC Morgan dollars feature some kind of overdate). Although this variety does not feature an underlying "7" within any part of the "8". There is a very subtle and small bar or dash under the "8" - which is the bottom of the underlying "7". The difference between the 1880 CC "Reverse of 1879" Varieties is depicted below in the example comparison image: