Here's an easy rule to apply when shopping for Aristocrats:
If the high E key touch is the same basic shape as the side C key, it's a student horn. (i.e. if the high E is flat as opposed to curved/angled up at the top like a modern horn).
You will generally only see the nickel plated keys on student model Aristocrats. The professional ones that are sought after generally have lacquer body and keys, though some early Aristocrats are fully silver plated.
If you are on a budget, you should look on eBay for a vintage Elkhart.
Most of these you see are Aristocrat clones (a few you will see are older "The Buescher" clones with splt bell keys).
This was Bueschers budget line, but the body, neck and all but a few cosmetics in the keywork are identical to (and interchangeable with) an Aristocrat. The big difference is that they do not have the snap-in pads, Norton gold-plated springs or amber-colored rollers. They rolled off the same assembly lines as the Aristocrats.