Fortunately, the game functions are filled with assert calls. They often include the file name, line number and function name and so are a real help with identifying loose code fragments and class member assignments.
dbsim.exe is generally different from the assert message style (most calls miss function names, and the source file names don't have a directory) from the vshell.exe assert messages (these do carry file names, but apparently this was another dev team or a totally different unit - or the engine was bought?).
So far, the following source files have been observed in the code:
armory.cpp (vshell)
base.cpp (dbsim)
beam.cpp (dbsim)
bullet.cpp (dbsim)
career.cpp (vshell)
classio.cpp (vshell)
ctxt.cpp (vshell)
collide.cpp (dbsim)
damage.cpp (dbsim)
debris.cpp (dbsim)
devices.cpp (vshell)
dv_jy.cpp (vshell)
dv_ky.cpp (vshell)
dv_mse.cpp (vshell)
esanim2.cpp (vshell)
esdialog.cpp (vshell)
esglobal.cpp (vshell)
esgrid.cpp (vshell)
esreport.cpp (vshell)
esquad.cpp (vshell)
esmsg.cpp (vshell)
explo.cpp (dbsim)
fileutil.cpp (vshell)
fire.cpp (dbsim)
game.cpp (vshell)
herc.cpp (vshell)
hercdisp.cpp (vshell)
hercinfo.cpp (vshell)
herclist.cpp (vshell)
hgrid.cpp (vshell)
init.cpp (dbsim)
flyersys.cpp (dbsim)
gunlist.cpp (dbsim)
libio.cpp (dbsim)
main.cpp (dbsim)
mechsys.cpp (dbsim)
mechview.cpp (dbsim)
msn_gen.cpp (vshell)
mymem.cpp (vshell)
objlist.cpp (dbsim)
panel.cpp (dbsim)
pdamage.cpp (dbsim)
phdd.cpp (dbsim)
prefs.cpp (vshell)
rocket.cpp (dbsim)
shellmap.cpp (vshell)
sound.cpp (vshell)
stats.cpp (vshell)
strings.cpp (vshell)
terrain.cpp (dbsim)
ts_part.cpp (vshell)
utility.cpp (vshell)
vcr.cpp (dbsim)
volume.cpp (vshell)
volgroup.cpp (vshell)
volrstrm.cpp (vshell)
warmingi.cpp (vshell)
wcrewi.cpp (vshell)
winstuff.cpp (vshell)
wmain.cpp (vshell)
warmoryi.cpp (vshell)
wmissini.cpp (vshell)
wsquadi.cpp (vshell)
wsrvbayi.cpp (vshell)
world.cpp (dbsim)
src32\gl_font.cpp (vshell) - maybe there are version-dependent src files
wsrc\ptrarray.cpp (vshell)
wsrc\window.cpp (vshell)
wsrc\winwin95.cpp (vshell)
inc\squad.h (vshell)
inc\esgrid.h (vshell)
inc\sfx_fix.h (vshell)
inc32\ts_base.h (vshell)
winc\ptrarray.h (vshell)
code\wwinbase.cpp (vshell)
code\wintimer.cpp (vshell)
include\whandler.h (vshell)
d:\include\ptrarray.h (vshell)