This picture (left) is from a 1933 article on the new 65, and is drawn from a LHD car. This 1935 car (below) shows the Lucas battery which has integral lugs/flanges to connect up with the retainer post on either side (shown here unconnected):
These ones (from the same car, photo taken 25 years later) have an Austin part number and several cars have brackets similar.
This photo shows the battery cover with the same brackets on a 1934 car.
This 1936 car had partial remains of one of the brackets on the other side of the battery box, and the two screw locations can be seen here, one underneath a newer surface. A central threaded rod replaces.