The Unicomp 122 key has 3 different versions, actually: 5250, 3270, and 5250/PC. It is my understanding that these are the Unicomp evolution of the 1397000. Specifically, when I called about them, Chuck told me that the 1397000 was actually the 3270 (unique scan codes on all the extra keys, but otherwise standard), the 5250/PC used the modifiers as described in the OP, and the 5250 was actually for specific hardware. Not sure how accurate that was, though. Sometimes I think Chuck just makes things up on the spot.
Somewhere on geekhack I've actually read that there is a jumper on the controller of these that actually switches it between the three modes.
Oh, and ch_123, these are the terminal emulators, not the actual terminal keyboards. They use standard PC scan codes, not set 3.
But, if you want a fully functional 122 key keyboard for a PC, there are several on ebay for less than a new unicomp. Search for 1397000. Also, I'm not sure what ch_123 is talking about in regards to the lock lights. All of mine (I have 4) have just worked. Though Ripster has one that didn't. Mine are all 1397000s, from different years. All send unique scan codes, as well.
You can definitely see the differences in construction in these better than in the 1391401s, though. The plate, for instance, has become visibly thinner as the years went on. All of them have a distinct amount of flex in the case though, as for whatever reason they are only held closed by 3 screws, rather than 4, so the sides don't sit flush the way they should. Not a big deal for me, and the Unicomps may have fixed that.
That said, I love mine. It's my default keyboard on both my work and home computers. I did switch the layout to be more similar to the HHKB, though, which I also use on the same computers.
