I bought about 10 of these from a customer. 9 of them look right for MS-63, good details, nice luster, a few bag marks, but this one looks like an XF coin, tops. The Slab does not look wrong, it is the right date and mint mark, it is a real cert, but the coin just looks bad. Plus it is only a $50 coin with the MS63 Grade anyway. Could it be a weak strike? The Rest of the look like this.
A lot of New Orleans Morgan dollars were known for a weak strike, but it was also believed that some of them were due to improper annealing. I don't know! I used to have 20 of the 1888-O Morgans graded MS63-MS65, and about half of them were weaker than your specimen. ~ Chris
I'm a little late to the party, but yes, weak strike. the metal isn't discolored from wear, it just didn't flow into the deepest points of the die when struck. If you sell it, it might not bring as strong a price from a collector who prefers a well struck coin, but someone who's buying the slab and not the coin isn't going to think twice.
I read somewhere that at the New Orleans mint, sometimes the dies were spaced just a tiny bit farther apart than optimal in the presses, in an effort to extend the life of the dies. Remember, they were running the mint as a metal stamping shop, and by the mid 1880s they knew most of the dollars they made would end up stored in bags rather than circulating, so keeping production running was a higher priority than ensuring each coin was fully struck.
Common for the year to look like that. Also normal for an O mintmark. If you think it's an XF coin, then you need to do some research.