Model M history lesson for you. The IBM Terminal Keyboard (the beast based off the Model M, which had a bunch of extra keys) was designed in 1984 and released/built the next year. The PC keyboard variant (the terminal keyboard will not work with a PC) was released in 1985. Perhaps he's surfing the net on an ancient IBM dumb terminal? Somehow I doubt that. ;-) They are the only ones that even have a chance of having been built in 1984, and to date, no one has come up with credible evidence of such - but again, they won't work on a PC. Different timing, different lots of things.
Anyway, a lot of people keep claiming their Model M is from 1984 because they are reading the copyright date (which is the same on all IBM Model M's and most Lexmark Model M's) instead of the "date of birth" spot which has the actual manufacturer date to the specific day (which is on all IBM and Lexmark Model M's). And of course, there are a few who keep trying to make such an incorrect claim, because claiming to have the oldest Model M seems to be a badge of fame in the Model M world.