The MCARDs clearly say MCARD in large letters on side with the text. If you don't see that, you have the older 'S' CableCards. I don't think there is any way to tell from the TV menu, you would have to pull it out.
As far as I know, Verizon didn't take any shipments of MCARDs until Motorola stopped shipping the older 'S' CableCards in April.
