The story has two versions - at least - about Truman's middle initial. Some say it has no period after it, and others say it does. The most recent scholarship that I've read says there is a period, and I've read that his tombstone also has a period after the S. Truman served just 82 days as FDR's vice-presidet, when Roosevelt passed away. Truman assumed office and was immediately faced with the decision to drop the first atomic bomb in Word War II.
Enjoy the cache. Park carefully. Be safe. Have fun!