Proving your birth

I was at Southern Thrift Store in Nashville yesterday, buying a couch for my office, when I looked up and saw a sign announcing a senior citizen's discount. It read, "Discount for Seniors 65 and up with Proof of Birth." Um, isn't the fact that the person is standing there a proof of birth? It could be that the sign used to say Birthday. For now though, it brought me a chuckle.