You may use this format which we use in our company
Sep 22, 2008
TO WHOMSOEVER IT MAY CONCERN
This is to certify that (Interns Name), a student of (College & University Name) did her internship at (Your Co's Name & Place) from (strating date) till (end date).
During this period (candidate's first name) successfully completed his / her project stint in the area of (Projest details or name/ Training details)
for (Your Co's name)
(Authorised Signatory Name & Designation)
24th September 2008 From India, Mumbai