I am 99.9% sure that the lettering on the intermediate sill was put there by the St. Charles Car Co. when the car was built. The top photo below shows the same lettering used inside the car, above the door. It looks like the same stencil was used. The bottom photo shows the white lettering applied inside the car by the C&S. The original black lettering can be seen to the right.
C&S 8027 was built by the St. Charles Car Company of St. Charles Missouri (near St Louis) in December of 1898, as part of a lot of 40 cars (8026-8064. The cars were ordered by C&S predecessor Union Pacific Denver & Gulf, but lettered for the C&S (the C&S came into existance on December 31, 1898). The cars original cost was $415 each ($85 less than I paid for its decrepit body 107 years later!). 8027 was retired in 1939 and dismantled, its body becoming a shed on a farm about 5 miles east of Boulder Colorado. I bought the body in March of 2005.
Jason Midyette