You can tell the date of manufacture by looking at the last 3 digits of the sensor serial number.  The first two digits are for the month and the last digit is for the year.  For example May 2012 would be 052.

Honeywell warranties these sensors for 2 years.  However, they have been having problems with this particular sensor not lasting the full 2 years, so they have been replacing a number of them under warranty.

These sensors come prepackaged in sealed clear plastic containers.

If you're sensor has died prematurely you will see ERR where you would normally see the Oxygen reading.