Vertu has released its Signature-model smartphone in a sleek new chocolate-brown version for fall. The Signature Pure Chocolate ($16,600) features the brand’s PVD-coated stainless-steel case and trademark sapphire-crystal keys in deep brown, with red-gold numerals. Handmade in Hampshire, England, the phone features Vertu’s complete range of services, including the travel-security feature Vertu Certainty and the Vertu Concierge service, which provides users with dedicated on-call assistance 24 hours a day. Each…