I remember seeing the ebay posting for this, and I think it was legitimate because the seller had some other rare Cas items, but I did not bid because it seems pretty easy for almost anyone to fake these.  There doesn't appear to be any info on how many were printed, any security features of the paper, etc.  And I doubt Mike will weigh in at this point.  So without some direct proof of the original purchase, I would not have any confidence in saying one is legitimate or not. 

Even in this thread, the two examples posted have lots of little differences.  One has a header showing "S/N", the other says "Seq #".  The fonts, spacing, and colors also appear to have some differences.