I plugged mine in and went through all the diagnostics. I also tried to update since mine was from '15. It appears that was the most recent firmware update. I had no idea what the rest of the numbers meant so I let everything alone.
Since the unit was introduced in 2014, and the next one came out in 2016, it's safe to assume that all the refurb/closeout deals will have the latest revision. Used stuff from Ebay and such might be another story.