Buying this stock truly is getting "a piece of the rock."For years, the top advertising slogan for Prudential Financial (PRU 0.36%) was "Get a piece of the rock." The global financial services and investment management company still uses the iconic image of the Rock of Gibraltar in its logo.I just got a piece of the rock. Instead of buying insurance or another financial product from Prudential, though, I invested in the company. Here's why I just loaded up on this dirt cheap, high-yield dividend stock.1. It ...