You can still try
cabextract and/or
gcab on it for the unlikely case it
is a Microsoft cabinet, but wasn't recognized by
file.
You can also try
7z if it's compressed in format recognized by 7z.
Newer versions of General CAPP use different format. I downloaded some and they show this:
Code:
$ strings -n3 file|head -2
GXD
Created with General CADD for Windows
I hope files in their old format (CMP) would show something similar.
Here they give more possibilities for what .cmp could mean.