That is an IBM Model M5-2. Unicomp makes them new, but for $109. I have a rubber dome version on the Unicomp, and the trackball actually helps save space, even if it is such a big keyboard.
And I disagree with CH_123, the tracking is perfectly decent, if it is too slow, just turn up the sensitivity. And the IBM M4-1 has a perfectly good trackpoint. I hate it when trackpoints move too fast, and the M4-1 has the perfect speed, not too fast, not too slow.