Any thoughts on this large backpack please

[CAnnUK]

Hi Guys, Not sure on what his backpack is, so I have put it in the attic finds section. No markings at all that I can find. Has anyone ideas on who made this and age of it. I am not even sure it is military but it looks the part and was in with other militaria. Not in the greatest of shape, so I need to find out what it is, so I can decide what to do with it. Backpack measures out to 30 inch by 20 inch . Thanks again! Neil.