Determine AutoCAD DWG file version.
The first 6 bytes of a DWG file will indicate the version used.
1. Open the DWG file in Notepad or Notepad++ (Recommended)
2. Compare the first 6 bytes against the following list to find out the version that last saved the file. Note: This may not be the same version that created the file.
AudoCAD DWG file version number
AC1027 AutoCAD 2013
AC1024 AutoCAD 2010/2011/2012
AC1021 AutoCAD 2007/2008/2009
AC1018 AutoCAD 2004/2005/2006
AC1015 AutoCAD 2000/2000i/2002
AC1014 Release 14
AC1012 Release 13
AC1009 Release 11/12
AC1006 Release 10
AC1004 Release 9
AC1003 Version 2.60
AC1002 Version 2.50
AC1001 Version 2.22
AC2.22 Version 2.22
AC2.21 Version 2.21
AC2.10 Version 2.10
AC1.50 Version 2.05
AC1.40 Version 1.40
AC1.2 Version 1.2
MC0.0 Version 1.0