I have no knowledge of rib adornment evolution. Early ribs were pattern welded metal, and they seems to have been fabricated with aesthetics in mind; frequently using disparate patterns
Laminated steel and stub twist
2 stripe and twist, refinished by Brad Bachelder
Attractive contrast
Parker Lifter with crolle and crolle
this is neat
but eventually Parker chose to matt the crolle ribs
Along with Syracuse Smiths, until Hunter Arms started using a steel rib
More examples here
http://www.picturetrail.com/sfx/album/view/21182597 
