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.
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
Article ID: 1162
Created: May 3, 2016
Last Updated: May 3, 2016
Author: GstarCAD Malaysia
Online URL: https://www.gstarcad.com.my/knowledge/article/determine-autocad-dwg-file-version-1162.html