This is a 2x12 box, definitely Australian, and dating from the 1960s.
After a fair bit of head-scratching and going back over countless photographs of vintage Australian amps I have sold over the years (and there are many!), I am 99% certain this is a Rex. It's definitely a 2x12 BA50 cabinet, as the input jack is stamped with this model designation (see the detailed photographs in the 'more pictures' link below).
The item came to us along with an equally mint Maxim bass amplifier, and both had been sitting in an office storeroom since the late 1960s! Not a damp garage, not lugged to gigs for 40 years, simply sitting in air-conditioned comfort all this time. As a result, the original Sydney-made MSP Hi-Flux 12" speakers are in as-new condition, and the cabinet has barely a rub mark on it. The nickel-plated corners are still as-new, and untarnished. Truly amazing.
This would be a fantastic guitar or bass cabinet to use with your 40-50 watt vintage valve amplifier. It's rated comfortably at 50 watts (with a 4ohm impedance, but I can re-wire to 16 ohms if you prefer), and sounds great with the sealed back.
Sold to Tony in Queensland