How common was it to receive a certificate from Zumwalt, and then another from Hyland? for the same medal.
Some editing at the approval level may take place for various reasons,
Was this not uncommon then? And would many of those who have posted their own citations, also have in their possession a second one signed by Hyland? which maybe they don't post?
Zumwalt was probably the approval authority and Lehman for the replacement medal.
Was there a form that someone had to send in to request replacements? Someone asked this, before. But what would it be? What document?
It is important not to confuse the citations with the certificates. There is only one certificate per award. As I indicated, there is a standard approval process. I presume Hyland signed the certicate as the approval authority as well as the citiation. Kerry has not released the actual certificates except for his PHs. Zumwalt signed the nomination form, including a draft citation on letterhead paper. Usually the nominator includes language for the certificate and citation on the form as well as a complete write up for the award. If you notice, Hyland only signed the Silver Star citation, not the Bronze Star. Zumwalt probably has approval authority for that level of the award as area commander. The Chief of Naval Personnel signed Kery's PHs certificates in August 1969, all on the same day.
Was this not uncommon then? And would many of those who have posted their own citations, also have in their possession a second one signed by Hyland? which maybe they don't post?
I don't quite understand what you mean by post. The citations and certificates are part of your official personnel record. When you receive the medal, you get a copy of the approved citation and usually the certificate at the same time. Sometimes there is a lag between them, but not often. The PHs seem to be that exception. Kerry has his personnel records so he can provide whatever he wants. Maybe he wanted both Zumwalt's and Hyland's signed citations on his Silver Star publicized.
Was there a form that someone had to send in to request replacements? Someone asked this, before. But what would it be? What document?
The Navy is a government bureaucracy so I am sure there is some sort of request process and form to get replacement medals. The form would be processed using Kerry's official military records. There is a DD215 request form to update your DD214. I suspect Kerry received expedited service as either a LT Gov or sitting senator. I don't know the form number to request replacment medals.