I don't believe the numbers reference the week...I beleive it is the Julian date and this has correlated to the time of year certain batch numbers have appeared. The number above tells me that this batch was produced on the 188th day of 2004. If you start watching the numbers I think you will see a direct correlation. For example, M050XXX appeared in Feb or March which would relate to a Jan or Feb production date (depending on which numbers followed the 050...0501XXX would indicate production in the second week of Jan...0502XXX, the end of Feb etc. This follows the logic of the sequence too as the time of day accompanies the designation of the specific Julian date, e.g. 14 Jan at 1055.