Lots of pictures would allow those who really know to provide an expert opinion.
Olive paint? Do a search of the website, you will find a few threads discussing the olive paint that should give you more information.
Sand and red soil may be found anywhere and isn't necessarily an indication of use. Desert, Middle East, Australia, India, Ethiopia, Somalia, etc
Battlefield pickup? I doubt if a GI would pick up on of the allied forces' rifles and try to take it back with him, but anything is possible with LE rifles. More probably an import. Only pictures of the markings will possibly tell.