case "AC1018":
header.ver = DwgVersion.R2004;
break;
case "AC1021":
header.ver = DwgVersion.R2007;
break;
case "AC1024":
header.ver = DwgVersion.R2010;
break;
case "AC1027":
header.ver = DwgVersion.R2013;
break;
case "AC1032":
header.ver = DwgVersion.R2018;
break;