Yeah, it's definitely a interesting lamp. The sleeve is a similar style to the ones my 1960s BT-25s came in so that's why I guess they were also from the 60s.
Oh and here's some stuff on Kiijii:
Powerlite gumball, looks to be newer than mine as the slipfitter is a separate piece and the latches are stamped instead of cast. Good price though. Not sure if bulb is still there but 300w mogul based bulbs from hardware stores work find in them.
70w HPS AEL 113 Comes with arm but bulb is missing.
Powerlite gumball like the first one but this one looks to be almost NOS.