Revell and Monogram merged in the mid-late 80's. (I also can't recall the exact date) Kits continued to be produced under both names separately, but there was some mold swapping and it became evident to the keen observer that design teams also started to share ideas.
Finally, the first kits labeled as Revell/Monogram appeared around the time of the indroduction of the ProModeler line by Monogram. There were now kits being marketed under four labels, Revell, Monogram, ProModeler by Monogram and Revell/Monogram. Soon thereafter, the ProModeler kits were labeled as ProModeler by Revell/Monogram.
Nowadays, I don't pay too much attention to this stuff anymore, but it seems as though the "regular" domestically produced aircraft kits (including some of the original ProModeler molds) are produced under the Revell label, regardless of their origin as Revell or Monogram kits.
The imported stuff (Hasegawa and Dragon molds) are marketed under the Monogram/ProModeler label. As far as other genres, cars and such, I dunno!
Fade to Black...