Coherent was a Unix clone for IBM compatibles Mark Williams Company produced and sold in the 1980s and early 1990s.
What environment and tools was Coherent developed with? Was it cross-developed on another Unix system?
Mark Williams Co. used a PDP-11 as development platform before COHERENT came up, once COHERENT booted all development shifted quickly to COHERENT-based.
MWC never had any Unix machine in-house. Some of the developers had previously used Unix at Waterloo.
Many thanks to Steve Ness for the information.
According to this article and a few others around the net, Coherent was originally written on and for the DEC PDP -11. It was then ported to other processors, including x86.