A. K. & Co.
From the Official Railway Equipment Register of 1901:
A. Knabb & Company was a cooperage business established in Warren, Pennsylvania during the Pennsylvania oil boom. The company manufactured staves for oil barrels, and became involved in the general lumber business in Pennsylvania and Maryland. The business was large enough to require their own railroad rolling stock to move raw timber and finished products.
Samuel T. Pees documents this rail car as likely that of A. Knabb & Company. Empty barrels are triple racked for transport from the cooperage to the buyer.