Was it plastic or metal (Titanium)? I've had a plastic card issued to me in the past without a chip as an emergency replacement card. If it is metal without a chip, then it is most likely a clone that seem to be available online. The word 'Centurion' should be in small text on the back twice - once under the white signature strip (Centurion Member Signature), and then in the box below - US card says 'Centurion Member Services available 24 hours a day', UK card says '24 Hour Centurion Concierge'.

The metal card should be in two pieces, the main card and then the insert on the back below the signature panel which is which goes over the embossed section (they hammer through the numbers), you should not be able to see the embossed numbers on the back (if you do, it is a fake card).