Lawful money appears as one and the same as Federal Reserve Notes. As David has quoted the Federal Reserve website, and as the Treasury.gov website states "United States notes serve no function that is not already adequately served by Federal Reserve notes. As a result, the Treasury Department stopped issuing United States notes, and none have been placed into circulation since January 21, 1971."
The point being that you make your demand via restricted endorsement on the back of the check and/or via the signature card on the bank account. Once your demand is known for that specific instrument, you have lawful money in hand. As David states, do not worry what the bank does behind the counter, you will get wrapped around the axle of the banks problem. It is not your problem. You have completed your requirement by making your demand.