When Did It Happen?

I was sorting through my coins trying to come up with exact change in the grocery store last week.  (In Romania, most cashiers expect and will even sometimes demand exact payment of a bill.)  I was shocked to look down and see a penny with a completely different reverse side than the one I'd grown familiar with.  According to the US mint website the design I'm most famliar with (Lincoln Memorial) has been used since 1959.  The new penny features a union shield with 13 vertical stripes which represent the states that joined in one compact union to support the federal government, which is represented by the horizontal bar above. The horizontal bar features the inscription E PLURIBUS UNUM—"out of many, one". The union shield, which dates back to the 1780s, was used widely during the Civil War. The shield is also featured on frescoes by Constantino Brumidi throughout the halls of the U.S. Capitol Building completed in the mid-19th century.