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