I'm thinking it is a legit replacement citation issued when Lehman was Sec of Navy. It probably is a rubber stamp signature. Mr. Kerry probably burned his original citations or threw them over the White House fence!
Again check out the folowing link for Service Ribbon Replacement program;
http://www.amervets.com/replacement/nmos.htm Note the following passage (well down the page)
"Establishing Authority
The Navy and Marine Corps Overseas Service Ribbon was estab-lished on September 17, 1968, by Secretary of the Navy John F. Lehman, Jr. and announced in OPNAVNOTE 1650 of June 3, 1987."
This site is not referring to Bronze star but if you look on the site you will find a link to the Bronze and Silver Star replacement citation pages.