It is possible that there may be more than one way to get at the same information. This can happen in two ways--copies of the original were made and reproduced, much like microfilmed copies of records may provide duplicates in several different areas.
More than one organization or group may have recorded the event. Death certificates, tombstones, and obituaries provide dates of death. Civil and church records may provide the date of a marriage.
Ask yourself are there duplicate copies of a record?
Ask yourself if there are multiple record creatores who might have created duplicate records of an event.