I posted this last year and am curious if anyone else has thought on the origin of this mint-sewn bag. http://www.cointalk.org/showthread.php?t=5977
Why don't you contact the Mint? If they don't know whether the "P" in the date stamp stands for Philladelphia (99.44% probability IMHO) or it doesn't, in which case the only way to find out what's inside is to open the bag.