The serial numbers hold no date codes. The slip of paper that is being talked about is usually between the outer box and the wood inserts that are used to form a lip that the box closes on located on the hinge side of the box.
Depending on how old they are, this paper slip may actually be laying in the bottom of the box under the cigars. Newer boxes, say in the last year or so are either in the bottom of the box or non existent, seems they arent as worried about or just dont have time to place date tags in all the boxes anymore, thats not to say it isnt there they just havent been as consistent as of late with the slips of paper.
If that 160... number was on the bottom outer part of the box written in sharpie, it is your local shops "identity" number with Padron and means very little or nothing to the consumer.