Here are some pictures of the 20rnd mag tin which holds 10 magazines and is a little smaller than the standard 30rnd Bren mag tin. I don't know the country of origin of this smaller 20rnd, 10 mag tin although, as can be seen, it now has English stencilled markings. I can see no maker markings visible and although there are no other markings clearly visible there could be some other markings under the paint. This small mag tin appears to be very well made and finished to a high quality. I have included some comparison photos with a standard British.303 Bren mag tin.
You can probably source the standard .303 Bren mag tin via eBay or elsewhere at a reasonable cost. The smaller tin is much less common in the U.K. although I still managed to purchase it at a sensible price.