I called CRO before I received the postcard, and I asked the CM if there was any way I could get a discount because I've read that many people had received postcards and emails. The CM explained that there would be a code/PIN listed in their computer system in my personal record if one was available to me. So he checked my record and there was nothing listed at that time.
A few days later I received the postcard, in my maiden name and current address. When I called CRO and gave the CM my PIN number, she called up my record and couldn't find a discount. So she searched by PIN number and noted that the PIN number is associated with a different last name. (I explained and she said it is fine....). So, yes, they can chart whether you've actually received a discount offer or not. At least they could with me so I'm assuming they can with others too. But I'm still bringing my postcard to checkin, just in case........