Maybe well off course here, but the following pic (
source) is of the rear cab wall of a canvas topped Aust RAEME Land Rover. It could well be that these two brackets are for the crew's SLRs, but RAEME chappies being as they are, it's possible the top one is for a L4A4 Bren. They bear a similarity to the brackets pictured by Bob, so I SURMISE they brackets are for the AALMG Bren.