Many record offices created indexes to their records as those items were recorded. These indexes are not perfect. They are not every name indexes. And just like with every index, names can get left out. But they do have some occasional advantages over new indexes created decades or centuries later to digital images of those records.
The “original indexes” created by the clerk or office that recorded the record originally were often created by the person recording the item at the time it was recorded. The handwriting was not faded. They may have actually known the individuals involved and were better able to render the name in the index even if it was difficult to read on the original–particularly if the original was a birth certificate written by a doctor or someone with handwriting that was difficult to read.
So if the “newer” index to records is not helpful and a manual search is not feasible see if there were indexes to the records created at the time those records were created.
And double check to make certain that a manual search is truly not feasible. Sometimes it simply takes time.
Many of these locally created indexes are included in FamilySearch’s set of digital images of records–see my webinar on those images.