The Lionel Mark Twain Zephyr is Pioneer Zephyr with different car names.
The Lionel model:
Notice the dip in the brow of the model. This was unique to only the Pioneer Zephyr.
The Prototype:
Plus, the Mark Twain Zephyr had a full baggage car Becky Thacher.
Rusty
Agreed - right on both counts but despite these discrepancies the Mark Twain is still a nice model. For the OP maybe you should check out Eric S's video review on http://www.ericstrains.com/video/index.php. He doesn't mention the way one car name was flubbed (although you can see it in his video) but then only purists may be annoyed by it given the way the model otherwise performs!