From: http://forums.apc.com/spaces/5/smart-ups-symmetra-lx-rm/forums/general/5802/how-to-tell-manufacture-date-by-serial-number-on-sybt5

Read Serial Number to find age of unit
Angela 3/5/2012 4:15 PM (in response to txrecycler)

An example of a serial number is below:

PD *1204* 235232

the 12 after the PD characters indicates it was manufactured in 2012 and then the 04 means in the 4th week of 2012. 

Also: http://www.nogeekleftbehind.com/2008/01/07/apc-ups-serial-number-trick/

Model # or “SKU,” from which the product family can be determined: http://www.apc.com/support/model_number.cfm