More significant* is that his work at Xerox is likely unavailable due to how Interlisp-D worked. When I started to work for Doug on Cyc he had a three-year old band (checkpointed image) he'd been working on continuously on the Dolphin in his PARC office. As you can imagine it was full of lost fossils in memory with completely unpredictable effects on the code. I'm certain that memory image has been gone fro any backup tape for almost 40 years.

Even though we'd overlapped at PARC, when I got to MCC (Cyc), for technical reasons I refused to even use the D machine version and started out with a blank zemacs buffer on a symbolics machine. One major technical reason is that you actually had source code which could be loaded into a fresh memory image. I made sure from the start that always worked.

* what makes it significant, to me, is the technical/cultural implication of the PARC "band" model of Smalltalk and Interlisp-D. I don't mean the early Cyc code base is particularly interesting in and of itself. Interlisp on the -10 usually used files of source code, as you referenced and you would be used to from CommonLisp.