Look around you. How many things near you have serial numbers? Almost anything technical or technological has a serial number. We take it for granted that many manufactured items have been numbered.
What can you do with those numbers? One story tells of how the allies in WWII were able to estimate the production of German tanks by collecting the serial numbers off of destroyed or captured tanks. There are a few variations on the story. Each has slightly different numbers in involved. In 2006 Gavyn Davies explained the math in the Guardian. If Wikipedia is to be believed there was additional math involved that even looked at an estimate of the number of molds the Germans had to make tank wheels.
What about using serial numbers in the present day? Is there information hidden in modern serial numbers? Could you get enough serial numbers to uncover this information?
The answers are yes, yes, and yes. Thanks to the internet it is easy to ask lots of people to type in serial numbers. Once there are enough of them... the investigation begins. Here's what can be found out from the serial numbers from a large number of Microsoft XBoxes.