Letter for payment to me!

I just received a letter in the mail (yesterday ...8/2) from FIA Card Services. Apparently a check for $161.40 was sent to me 9/2006 that was never presented for payment and that this was my money and all I needed to do was sign a paper and send it back to them within 30 days of the date of the letter. The letter is dated 7/9/12, postmark is 7/30 and I received it 8/2.
Of course since this is 6 years ago, I don't remember this. I'm pretty sure that if a check had been sent to me, I would've cashed it. Anyway, I didn't recognize FIA Card Services so looked them up to find they bought out MBNA which I did have an account with.
After seeing the reviews of this terrible company,I'm honsetly quite wary of what this is about.
Is this a scam? I've read how they've gotten into people's accounts illegally to get money.
This letter requires that I sign my name and date it, which leads me to believe that once they have my signature, they will try anything to get to my bank account.
Has anyone else ever heard of this? Any advice? If it's legit, I only have a couple more days to send this in, if not...I'm not out anything and won't be terribly heartbroken!