During the 2004 election, I saw a piece on Fox News where they were aboard a Navy ship, and showed footage of a voting area set up and the on board post office actually running the ballots through a post marking machine. They wanted no doubts that the military ballots were date stamped by election day. I know what I saw. I will research further however and get back to you, if you still have doubts.
The Great Commonwealth doesn't work that way. The votes have to be received , not postmarked by election day. The votes are in that are going to get counted.
In fact, even upon being "invited" neither the Department of Navy nor the Florida Republican party would APPEAL the postmark decision to the USPS for ajudication ~ and BTW, it's USPS that's in charge of that, not Florida.
If they want time and date they can ask for it, but they cannot direct that a "postmark" provided by USPS be provided.
That, is, in fact, why this can still be an issue.
If Navy wants to do time and date stamping, that's up to Navy. The post office on board a ship is operated by Department of Defense. It's supposed to adhere to USPS rules. I don't think they can yet demonstrate that they do so.