Front carpet strips: let's figure this out

[DeadheadNM]

I'm curious if there is any rhyme or reason to the use of the differing styles of front carpet strip. One style is the " ribbed" strip that was also used as the rear carpet strip. The other style is "flat" with a sort of chamfer along the front edge at about 45 degree angle. Borrowed example pics attached.

For those owners who are reasonably certain they have the original front carpet strips I'd like to know:
1) model year
2) factory (Flint or St Louis)
3) double or single wall top if a 1972 model year

I've got:
Flat - 1972 Flint 1x wall
Ribbed - 1972 St Louis 2x wall