This article describes the categories of criminals who steal from jewelry stores. Employees who steal are obviously called “inside” thieves. Then you have “kleptos,” which are customers who steal for no apparent reason (kleptos are sometimes even long-time customers who certainly have the means to buy what they take). And then there are the professional thieves, the “sneaks”:

The “sneaks” generally travel in a party of three or more, enter a store as strangers to one another, and by a pre-arranged plan succeed in getting as many of the clerks as possible engaged in conversation at some point furthest away from where the diamonds and other valuable articles are located. Then the light-footed and deft-fingered member gets into action, makes connection with the wallet, tray of diamond rings, or the safe — frequently left unlocked during the day — secures the booty, and is off like a shot.

As a rule “sneaks” are well dressed — many of them them are so well groomed that they might be in a respectable line of business, and some even appear to the manner born. Therefore it behooves every jeweler to be on the qui vive.”

Read the article to learn about “pennyweighters,” and “yeggmen,” and scams like the half-eaten apple scheme (“an old one, but even now worked successfully in the smaller cities and towns”).

JEWELRY STORES ARE MAGNETS FOR THIEVES: Ruses Resorted to by Various Kinds of Crooks to Steal Precious Stones and Other Valuables and Escape Arrest (PDF)

From May 22, 1910