Within the multiverse of Marvel Comics, each iteration of Earth is given a numerical designation that serves to represent that universe. Earth-120185 is the universe in which the UK-published incarnation of the Transformers comic book series occurred. It is, at its core, largely similar to the Marvel US series, but with many additional events, and some divergences, most notably the story behind the reconstruction of the Autobot Bumblebee into Goldbug.
The essential difference between Earth-120185 and other universes in the Marvel Multiverse is that it became the battleground for the war between the Autobots and Decepticons. There are some elements that exist in some form (although not exactly the same form) across both Earth-120185 and the mainstream Marvel Universe (Earth-616), such as Spider-Man, Reed Richards, Nick Fury, Dum-Dum Dugan, (presumably) Godzilla, the Savage Land, U.S. 1 and Dazzler, but for unknown reasons, these beings did not factor into the later stages of the Transformers' war. Earth-120185 is also home to Action Force.
Per the original state of its timeline, the 21st century of Earth-120185 saw Unicron attack Cybertron in 2006. Following Unicron's defeat, the Galvatron of this era travelled back in time to 1987 and remained there for two years, ultimately resulting in a rift in the fabric of space and time that destabilised the universe. Although this rift was eventually sealed, Earth-120185's timeline was left permanently altered, its future warped into a dark shadow of its former self and diverged off from the primary timeline, becoming an alternate universe of its own.
The adventures of the Autobot Earthforce does not take place on Earth-120185 but a further divergent Earth.
Earth-120185 was given its name in the 2006 edition of the Official Handbook of the Marvel Universe, in the profile for Death's Head. It derives its name from January 12th 1985, the publication date of "Man of Iron!", Part 1, the first UK-originated comic. It is a common method to numerically classify universes of the Marvel Multiverse by dates like these - therefore we might theorise the universe depicted in the Marvel US comics to be Earth-984. However, Marvel Database calls it Earth-Transformers.
- Earth-120185 at Marvel Database