Original "hand laid" fiberglass was used on very early 1968 Shelbys. Probably only cars built before 15 December.
Here are some tips on identifying it:
Usually a greenish color. Mounting studs are in square blocks that are bonded with a red glue. The same glue used on GT500 KR hoods. They also have a rough textured back. The most common hand laid part is the lower valence. Most likely AOSmith had not completed the mold and was forced to use several hundred of these parts.
If you dont see these features, you are dealing with a reproduction.