The New York times did a video analysis that pretty convincingly showed it was a bullet. Why Trump is hiding evidence is just bizarre, like the idea of having to support anything he claims - even true things! - is offensive.
https://www.nytimes.com/2024/07/26/us/politics/trump-shooter-bullet-trajectory-ear.html
It’s intended as a “this is the John Doe I’m talking about” kind of id, not a “the person with this card is John Doe” kind of id.