An iteration on the earlier Curiosity class, the Perseverance class was Starfleet's most advanced design when it was introduced in 2390. Emmett Till was among the first vessels of the class commissioned, under the command of Captain Ezri Dax.

The ship was the first to venture beyond the remnants of the fractured Romulan Empire, greatly expanding the Federation's knowledge of the far reaches of the Beta Quadrant; making first contact with 8 new warp-capable species in the process, two of which established formal diplomatic relations with the Federation not long after.

• The Emmett Till was created for the DS9 retrospective documentary 'What We Left Behind', shown in a hypothetical season 8 of the show. The exterior of the ship was designed by John Eaves, and can be seen in more detail here.
  
• The registry and ship class are conjectural of my part. One of Eaves concept pieces for the ship has the registry 'NCC-2277', so I simply added an 8 in front of that number. As for the class, 'Perseverance' illustrates the long road still ahead of us to reach a future where we learn from history rather than willfully forget it. Perseverance is also the proposed name for the next Mars rover, which will be similar in design to the rover Curiosity. Hence, I think the name also works due to the similarities this starship design shares with the Curiosity-Class from 'Star Trek: Picard'.
  
• The ship was named after Emmett Louis Till, an African-American boy who in 1955, at only 14 years old, was brutally lynched by a white mob in Mississippi, USA. As DS9 producer Ira Steven Behr (who named the starship) put it: "It seems to me that in order to reach a complete and healthy society we need to do two things. One, the historical record is broken and needs to be fixed. There’s lots of information floating around, but very little context. The past is no longer even prologue, it’s pretty much ignored. Two, we have to own our mistakes, our failures. Again, it seems to me that unless we recognize and remember our mistakes, embrace them, we are doomed to repeat them over and over and over again. Say hello to the 21st century. So, if I’m living on Federation Earth 300 years from now it would make me feel good to know that as Starfleet sails among the stars Emmett Till is sailing along with them. He is remembered. We own his story. He is part of our journey".