It looks to me like that started its life as an Indian Mk3 Bren and was converted to 'L4A1' spec - without the magazine support inserts - in 1970. Without mag inserts and A1 ejector block with HODevice made the gun doomed to fail. Which it did! Replaced with the superb A2 which also used L1A1 rifle and later 30 round specially made magazines. I would disagree that only a few thousand were made......... Enfield were churning them out until the late 70's
But I could be wrong of course