I can confirm that it works as per I use one on my XT. There are some
black cables for the Ms which have the 5-pin DIN although adapters do
work on the more common PS/2 cables. The one I have here is a 1390120
(Determinable from the lack of LEDs the 1390131 has and the silver
badge later models lack). The 1390131 which has LEDs also works fine,
I've tested as I own one as well.
Here's a picture of one on my XT:
http://goput.it/i05.jpg