The missing a is just a print defect, or as Doug likes to call them, "glorified" dots...or lack thereof. I think the a has to be mostly missing before it gets slabbed as one of the variations---mine below was graded PSA 7 Herrer...but like Doug I am not a graded guy nor aspire to same. By the way, the 57 Bakep and 52 Campos black star and missing front border are also likely just more of Doug's glorified stuff:
