American car maker GM has just completed a very impressive milestone. A half-billion vehicles over 106 years equals billions in commerce, payroll, investments and infrastructure in communities all over the world. For customers, these vehicles played roles in weddings, family vacations, graduations, new businesses and countless milestones along life’s journey. Globally, more than 500 million General Motors-branded vehicles have been built – the most of any automaker by far – and the company is putting its customers at the center of the accomplishment. GM CEO Mary Barra and GM North America and Global Chevrolet President Alan Batey celebrated the milestone Monday with customers, employees and dealers at the Fairfax Assembly plant in Kansas. Barra also announced that in the third week of May, all U.S. salaried and represented employees and retirees can share a one-time Customer Appreciation Discount. The discount can be combined with other incentives.