This Morgan has an invalid cert number...spoke to the seller and PCGS. I am curious to know what the story is.
Are you certain of that slab's authenticity? I'm not. (That does, of course, implicate the coin as well....) I would call PCGS and talk directly to them. Obviously, if it is fake you want to get your money back, but PCGS may be able to help with that. Of course, it may also just be a database error - which PCGS can help you with as well.
I did speak to PCGS and they do not recognize the slab...as well as the seller, Have not heard anything back from either.
It's interesting that they list coins with cert. numbers just above and below the number on yours. I'm thinking it's just an error.
I don't see anything wrong with the slab or coin. Is it a Rev. of '78? Database glitches like this happen all the time. The serial number is old enough where it could have gone through several sellers. E-mail them a picture of the front and the back. The last time I had this problem with one of mine, I took it to a show with me and one of the people at their booth spent a bunch of time on the phone with the mother ship and got it straightened out.