Index: Quake/gl_model.c
===================================================================
--- Quake/gl_model.c	(revision 508)
+++ Quake/gl_model.c	(working copy)
@@ -386,6 +386,8 @@ void Mod_LoadTextures (lump_t *l)
 	extern byte *hunk_base;
 //johnfitz
 
+	extern cvar_t r_externaltexture_fix; //mk
+
 	//johnfitz -- don't return early if no textures; still need to create dummy texture
 	if (!l->filelen)
 	{
@@ -437,7 +439,17 @@ void Mod_LoadTextures (lump_t *l)
 		if (!isDedicated) //no texture uploading for dedicated server
 		{
 			if (!Q_strncasecmp(tx->name,"sky",3)) //sky texture //also note -- was Q_strncmp, changed to match qbsp
+			{
+				//mk -- begin
+				if (r_externaltexture_fix.value) {
+					if (strstr(tx->name,"sky4")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==13039)
+							strcpy(tx->name,"sky1");
+						Con_Printf("  using %s\n", tx->name);
+					}
+				} //mk -- end
 				Sky_LoadTexture (tx);
+			}
 			else if (tx->name[0] == '*') //warping texture
 			{
 				//external textures -- first look in "textures/mapname/" then look in "textures/"
@@ -479,6 +491,52 @@ void Mod_LoadTextures (lump_t *l)
 				//external textures -- first look in "textures/mapname/" then look in "textures/"
 				mark = Hunk_LowMark ();
 				COM_StripExtension (loadmodel->name + 5, mapname);
+				//mk begin
+				if (r_externaltexture_fix.value) {
+					if (strstr(tx->name,"plat_top1")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==24428)
+							strcpy(tx->name,"plat_top1_cable");
+						else
+							strcpy(tx->name,"plat_top1_bolt");
+						Con_Printf("  using %s\n", tx->name);
+					}
+
+					if (strstr(tx->name,"metal5_2")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==49173)
+							strcpy(tx->name,"metal5_2_x");
+						else
+							strcpy(tx->name,"metal5_2_arc");
+						Con_Printf("  using %s\n", tx->name);
+					}
+
+					if (strstr(tx->name,"metal5_4")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==20977)
+							strcpy(tx->name,"metal5_4_double");
+						else
+							strcpy(tx->name,"metal5_4_arc");
+						Con_Printf("  using %s\n", tx->name);
+					}
+					if (strstr(tx->name,"metal5_8")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==48444)
+							strcpy(tx->name,"metal5_8_rune");
+						else
+							strcpy(tx->name,"metal5_8_back");
+						Con_Printf("  using %s\n", tx->name);
+					}
+					if (strstr(tx->name,"metal5_8")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==48444)
+							strcpy(tx->name,"metal5_8_rune");
+						else
+							strcpy(tx->name,"metal5_8_back");
+						Con_Printf("  using %s\n", tx->name);
+					}
+					if (strstr(tx->name,"window03")) {
+						if (CRC_Block((byte *)(tx+1), tx->width * tx->height)==63697) // e4m2 variant
+							strcpy(tx->name,"window03_e4m2");
+						Con_Printf("  using %s\n", tx->name);
+					}
+				} //mk end
+
 				sprintf (filename, "textures/%s/%s", mapname, tx->name);
 				data = Image_LoadImage (filename, &fwidth, &fheight);
 				if (!data)
Index: Quake/gl_rmain.c
===================================================================
--- Quake/gl_rmain.c	(revision 508)
+++ Quake/gl_rmain.c	(working copy)
@@ -102,6 +102,7 @@
 cvar_t	r_nolerp_list = {"r_nolerp_list", "progs/flame.mdl,progs/flame2.mdl,progs/braztall.mdl,progs/brazshrt.mdl,progs/longtrch.mdl,progs/flame_pyre.mdl,progs/v_saw.mdl,progs/v_xfist.mdl,progs/h2stuff/newfire.mdl"};
 extern cvar_t	r_vfog;
 //johnfitz
+cvar_t	r_externaltexture_fix = {"r_externaltexture_fix","0", true}; //mk
 
 cvar_t	gl_zfix = {"gl_zfix", "1", true}; // QuakeSpasm z-fighting fix
 
Index: Quake/gl_rmisc.c
===================================================================
--- Quake/gl_rmisc.c	(revision 508)
+++ Quake/gl_rmisc.c	(working copy)
@@ -44,6 +44,7 @@
 extern cvar_t r_lerpmove;
 extern cvar_t r_nolerp_list;
 //johnfitz
+extern cvar_t r_externaltexture_fix; //mk
 
 extern cvar_t gl_zfix; // QuakeSpasm z-fighting fix
 
@@ -241,6 +242,7 @@ void R_Init (void)
 	Cvar_RegisterVariable (&r_lerpmove, NULL);
 	Cvar_RegisterVariable (&r_nolerp_list, R_NoLerpList_f);
 	//johnfitz
+	Cvar_RegisterVariable (&r_externaltexture_fix, NULL); //mk
 
 	Cvar_RegisterVariable (&gl_zfix, NULL); // QuakeSpasm z-fighting fix