Here's something one doesn't see all that often... This cover was mailed from PENNSYLVANIA 5 December 1941. To date I have been unable to find an explaination for the 'obliterator' use (within the circular portion of the post mark), nor the censoring BEFORE the attack on Pearl Harbor. No other similar examples - from PENNSY or ANY OTHER ship at Pearl Harbor during this timeframe - have been reported.
BTW, this cover was given to me by the recipient! He lives not far from me, and the cover was mailed by his father.