Yes, I do believe the engines were produced in different years with different names. Both have an on/off switch under the cab for smoke but only one has an on/off switch for run/lock for direction. Williams has a nice parts list but shows only one type tender connection even though the two tender connectors are clearly different. I will call their parts department to see if they can tell me how to tell which of their engines have the run/lock switch before I purchase. Thanks for the reply.