In the picture of the article, it's a beige label, all the RD variants I know of are fixed cable blue label lexmarks.
Though interestingly enough, it's clearly a terminal board. You can just see the connector in the image. It's blurry but it's definitely not PS/2. Also, the split + on the tenkey gives it away. It won't work on a modern computer at all without a soarer converter.
Watching the first episode now, they appear to have replaced the "enter" key, but the tenkey also shows the cool legends. I like to think of them of symbols you use to make fences and borders in text-art programs.
edit: two different keyboards. The tenkey is clearly normal as you see him moving his mouse past it (in slow motion) at 7:12. Though it's still a terminal M (split plus sign). If you note the colour of the keys replacing the = sign. pebble!
You can see that modular connector at 9:32 after he gets accepted. Notice the legends are the cool fency ones and the split + keys are pearl.
edit: episode 2 at 9:35, you can see him cleaning his spacebar with a Q tip. As the camera pans across the keyboard, you can see a spring in the barrel, and some nasty board chow. Why isn't he cleaning that? Also the F keytop is missing.
The Esc is print printed as "del F". I'm not familiar with that keycap. If anyone here has some, we can probably pinpoint his terminal M more precisely.
edit: so when they break that M in half at the end (hah!) it's the one with pearl = legends so he has a spare. I expect the average viewer to notice this, and expect it to make a return as Chekhov's keyboard.
I would also like to note that the M's case is cracked when you see him resting it on the dumpster so they probably had it already sawed apart when they started.
Now if it were a 1390120 he would have had a much harder time breaking it up like that.
