You can use the following methods to find out whether the D.A.P. you are using is real or not:
Method-1: Take some granules of D.A.P. on hand and mix with lime properly if it is difficult to smell, then understand that it is real D.A.P.
Method-2: This is a very simple method. Take some D.A.P. granules in a hot pan and heat on slow flame if these granules start increasing in size then these are real.
Its rigid granules are gray and brown in colour and do not break easily with nails.