I have the English DOS CD version. I'm fairly certain it's the US version. I believe the file was TESTBED.SHP and was on CD1.
I haven't found that file on my 16.0 German Privateer 2 CDs, and the GOG releases also don't contain it. If you have time, can you check if your DARK.EXE contains the string "TESTBED.SHP"? If so, maybe we can figure out if it's possible to actually access that screen from within the game (but maybe it's just a leftover file and isn't referenced in DARK.EXE at all).
An interesting find in any case.