mtl file was close to mine, but yours work and mine not!

the mirror effect is not created in the [font=courier new]mtl[/font] , it's created in the [font=courier new]obj[/font] -file.
You can open the [font=courier new]obj[/font] -file in any text editor, same as with the [font=courier new]mtl[/font] -file.

Then you will see what creates the mirror effect.

Cec