DCS Diversified Collection Services Seemingly invalid debt collection attempt Livermore, California

I just received a letter from Diversified Collection Services, a debt collector located in Livermore, CA. They inform me they are attempting to collect on a defaulted student loan. This may very well be true, but the last student loan I obtained (and which I did default on (long story) was in 1990. As this is indicated to be a bank loan, and not a government loan, it would appear that the statute of limitations more than likely passed some fifteen years ago, as it is indicated as coming from a bank in NYC.

Although their mailing looks very professional, based on the other reports on this company here, I do not hold out much hope for reasoning with them; however, I have drafted a letter to assert my right to force them to confirm the validity of this debt in providing me with the name of the original creditor, what the debt was for, how it was referred to DCS, proof that the statute of limitations has not expired, and so on. I will be eagerly awaiting their response, but I'm not holding out much hope. We'll just have to see, I guess.