William, If you don't know, then it's time to ask what you don't understand. Not everyone is 100% knowledgable about all aspects of the many gauges, older trains (prewar), up to the newest generation with remote controls. You just need to ask, and you should get an honest answer.
As far as whistling tenders, some are marked with the number on the bottom, others aren't. For one not marked with a number, just look for a contact roller on one of the trucks, possibly on both trucks, or in some cases a central mounted roller pickup with wire going inside the shell. If you see that, it is a whistling tender, and the weight of the tender is obvious when holding both types.
I suspect you like Prewar, and you may want to try and get your hands on Greenberg Guide on Prewar Operating & Repair. That would be a good start. Good luck.
