If the paint is really thick it could be a later NOS part. All the later made NOS parts after 69 where painted and not finished. The paint is really thick unlike the repop.

The OEM header was a dull finish not paint. The aftermarket repops, have CCH stamped on the end (at least the ones I've seen) where the bracket mounts.

I had mine refinished. It is not exact but will hold up better then paint.