* According to the good folks at www.cybersax.com, there were at least two versions of the original "Top Hat & Cane": it had a different bell taper and tilt. Read all about it and see some good pics HERE. (They also have a feature regarding the restoration of a 400 there, too.)
* Note something about the serial number and model number ranges above. There were two horns called "400" that had the Top Hat and Cane engraving, but had different model numbers -- and then those model numbers were recycled for the Super 400. Additionally, there is significant evidence to indicate that the TH&C, Super 400 and the "Post Top Hat" 400 were all available at the same time. This might indicate that you could get 400's at different price points, with the "Top Hat & Cane's" beauty being at the top of the rung.
After all, what's the difference between the Super 400 and the TH&C? The S400's only available in the two-tone finish of lacquer with nickel-plated keywork and it had a nickel-plated tone-ring, rather than a silver one. And, of course, different engraving.
Oh. Also note that while the "Post TH&C" is a decent hornm, when someone is talking about the greatness that is the 400, he's talking about the Super 400 and "TH&C". The Selmer instruments are considerably lower quality.
* There are Super 400 sopranos. These are produced by Yanagisawa and were produced under Selmer's ownership.
* Like the Aristocrat of the same era -- and prior to Selmer's cheapening of the 400 line, these horns also had gold-plated Norton screw-in springs.