Find the DWG version

To find the version of a .DWG file, open the file in Notepad or some other ASCII or HEX editor and read the first six bytes, then reference the info below:

DWG Version

AC1032 = AutoCAD 2018
AC1027 = AutoCAD 2013
AC1024 = AutoCAD 2010
AC1021 = AutoCAD 2007
AC1018 = AutoCAD 2004
AC1015 = AutoCAD 2000
AC1014 = AutoCAD 14
AC1012 = AutoCAD 13
AC1009 = AutoCAD 11
AC1006 = AutoCAD 10
AC1004 = AutoCAD 9
AC1002 = AutoCAD 2

More info:
AutoCAD Release Timeline
AutoCAD Release History