Identification method
1. For an OptiX OSN 3500 NE, check the bar code on the fan assembly, which shows that the fan assembly was produced in 2005 or earlier. According to the bar code, numerals 12 and 13 represent the year, numeral 14 represents the month, as shown by the red underline in the following figure. "059" indicates that the fan assembly was produced in September 2005