Found two relevant entries for inverse video in the Systemhandbuch Teil 1:

p.158 shows a simplified diagram of the video circuit ... a "inverse" signal is coming out of the 8041A

p.106 the TDS (test and diagnostics system) disks have a test for the function of inverse video

NCR DMV- DEC Rainbow- Siemens PCD- ITT 3030-Oly People- Acorn A5000- Olivetti M20