First part indicates that the concerned person belongs to a community listed as OBC.
The second part indicates that the candidate does not fall in the creamy layer.
While the OBC status of a candidate may change only when the community of the concerned candidate is removed from the OBC list, In view of it, it is not possible to determine a fixed validity period for the OBC certificate.
Non Creamy Layer certificate issue between 1st April 2012 to 31st March 2013 is valid for 01-04-2012 to 31-03-2013. (i.e. financial year 2012-2013). After that you have to take New one.NCL is valid for one Financial Year.