Here are pictures of the two styles of 351C "Shelby" valve covers:
I personally have never seen one without the CS logo - but I found this picture on the 'net. I believe the ones without CS are late reproductions, the originals, and earlier reproductions, all had CS SHELBY lettering. Originals also have
oil splash deflectors in them. Many of the early repros have the bosses, but they were not drilled to mount the
oil deflectors.
regards,
Jeff