“Secrets?” Lane Schiffman pauses, mulling the question. “The fact is,” he says, “I don’t think we have any secrets.”?The fourth-generation­ jeweler is sitting in his office at Schiffman’s, a downtown fixture in Greensboro, N.C., since 1893. While he chats with a reporter on the phone, he’s got one eye on the front door the other on the sales floor. If any shopper has a sudden desire for that special Schiffman touch, he’ll have to call back.The conversation continues, but Schiffman has made his point. He and his brothers, Vance and Arnold Schiffman, pride themselves on their transparency and availability—not to mention their congeniality, which can turn strangers into friends the moment they walk through the door.All hold the title of vice president. Lane focuses on sales and marketing, Vance is the diamond buyer, and Arnold is chief financial officer. They oversee