Industrial Locomotive at Walkersville Southern

I just recently rode on the Walkersville Southern Railroad (delightful little line, highly recommended for a nice short ride for the family), and I noticed the locomotive, a PLymouth, I think, or maybe a Davenport, said Caterpillar on the radiator shell. Is this the type of engine that was installed, or did they help construct the locomotive? Or further more, did they make industrial switchers??
Thanks a lot!
Keith