TX = 275/270
Pro = 325/310
There should be a 102xxxx item identification number on the PCB. You'll have to look on ATI's site or contact them.
p.s. the TX is currently an OEM card by Dell, as you may well know already and has no retail box.
Again I think you will have to find some sort of identifier on the PCB to know for absolute certain what card you have.