One of the jobs of the Secret Wars series was to do away with the 616 sobriquet for the Marvel Universe, created by Dave Thorpe/Alan Moore for Captain Britain, picked up by Chris Claremont for the X-Men and eventually infecting the whole of the Marvel Universe. It was a good gag, while DC Comics obsessed with Earth 1, Earth 2, Earth 3, the Marvel Universe was a world outside your window, nothing special, much further down the dial;, and a lot more confident with its status.
As Marvel developed further dimensional realities, they all got their own similarly long numbers and as Marvel published the Ultimate Universe, so fans distinguished between that and the "616" universe.
Marvel execs and editors seemed to have an antipathy to the use, seeing it as bogged down in fanboy excess and off-putting to the casual reader. But in the year before Secret Wars, its use increased, principally by Dan Slott in Spider-Verse and Jonathan Hickman in Time Runs Out. Secret Wars put an end to all realities, then rebooted them, with the Marvel Universe no longer 616 but Prime.
Since then, apart from a few editorial mistakes in Web Warriors, Spider-Man and Spider-Gwen, Marvel has stayed pretty united on this. No one uses the 616 numbering.
No one, that is, except Brian Bendis, in today's Invincible Iron Man #8. With Stefano Caselli and Marte Gracia.
Weapons Of Mutant Destruction #1 by Greg Pak, Mahmud Asrar and Nolan Woodward is all up in that as well. Rather good too, especially for X-Men readers feeling X-Men Gold is a little lacking today…