I am aware that the armor is the same, but it's likely the museum would include a replica or demilitarized version of the original Mark VI armor from Halo 2 and 3
. I mean if they went through the effort to get all of the other suits, they'd probably try to fill in the missing link wouldn't you think? If not, that's a huge part of the story missing. Otherwise, people would be wondering what the armor looked like before Cortana's upgrades.