Doesn't look like WWII. I have never seen one of these. Looks a bit like a cape.
What material does it appear to be made from?
WWII era ponchos were made from a lined rubberised material like this one.
Sorry I can't be more help.
"Knowledge rests not upon truth alone, but upon error also."
Well I inspected this a bit more closely, and found a manufacture stamp and date of 1945. I then found another one of these which was identified as a British Army Monsoon cape as issued to troops in Burma and India etc in the book on page 88 of Khaki Drill and Jungle Green.
Attached is a photo of the stamp.