Tax Rebate checks!?

Where are the tax rebate checks coming from? Is it the State you live in? I just got a check for $752.00. Well, I am married and I know that married couples get up to $1200.00, that's up to $600.00 a piece. My husband paid in enough in tax because he gets paid alot at work and we filed jointly, well, they are suppose to send the checks out in July based on the last 2 digits of his social security number, since he is the primary tax payer on our checks. Well, the check came to us today and it was the amount I said in the beginning and it had my name first and it came in an envelope that was addressed from the state we live in, no explanations, just the check and we didn't recieve a letter about the check before it arrives and we have 2 kids, that we claimed in our taxes befor without any problems, one is a foster child that we are adopting and one we adopted last year. So, we are wondering what's the deal or if this is accurate or what? I know bill collectors can't any of the money