Weight, manufacturer, type of rail, etcetera.

We still have some Carnegie Steel Corporation rail, circa 1890s, here in
Monterey Bay.

(Carnegie and Mellon were later merged to form U.S. Steel Corporation).

I've seen some Geneva (a WWII-era plant near SLC) rail around here.

Since 1936, rail has generally been Controlled Cooled, and CC is usually seen
as a type marking.

Pre-1936/non-controlled cooled rail is highly favored by Gillette Company, for
use in razor blades.