Believe they are from the 1960’s, available in Australia.
I find the article Bricks on Display: a collection of interlocking building bricks on brickset to be a good source of information for this kind of question.
These appear to be Montini bricks (made by Berco Lux in Tiel, Holland, in the 1960s, as a clone of the early Lego Mursten) :
(images are from that same article)
The name of the brand should be engraved on the surface somewhere (between the studs afaict) - can you find it ?