See #69.
With records (including birth records), it is the original documents that are meant to be both the backup and authenticator of computer records.
I would be surprised if records like Immigration entry records, whose number far exceed those of once in a lifetime records (birth/death) would have ever been stored in duplicate. I would be even more surprised if the "coincidence" that caused only the 1 week of records around Obama's birth did not cause that same week to disappear for any duplicate records that might have existed.