Here's something new I found out
In some, not all of the rsd files,
there are snippets like the one below from
afbf.rsd
@RSD940102
# Output by SGI RSD fileset library libRsdObj.
PLY=AFCA.PLY
MAT=AFCA.MAT
GRP=AFCA.GRP
# Texture files
NTEX=0
Notice the # signs?
They descibes "Output by SGI RSD fileset library"
Not surprising that they use SGI, but does that mean all the stuff is done in the same manner? Sorry if this sounds stupid but can't help it, lack of knowledge.