I bought this second hand decades ago when I had (and used) an SLR camera. Those were the days. I never actually used it and it resurfaced in my old camera cupboard so I thought I would test it and pass it on to a good home.
Took out the six AA batteries in the handle,, spring contacts ok, not corroded. I put clips onto the battery springs (final - &+ ones right at the bottom) and connected to a current-limited PSU set at at 8.5v (equivalent to the 6 AA batteries in series). Half an amp was drawn, reducing to 0.1 amp once the discharge capacitor was charged. Ready light fired up.
Shorting the contacts on the connector to a camera caused a massive flash, which repeated half a second later. It was somewhat brighter than I am used to from ancient flash guns. So I can presume that the device is in working condition. The last 3 pics are of this process, including one with the appropriate lights on.
I do not have the short arm which can attach the flashgun to the SLR tripod mount, nor the colour filters which came with it when new.
On one side is a socket which I think is for an external power source. It would need it as the charging current was 0.5 amp and standby current 0.2 amp which would wipe out the AA internal batteries in quick order.
I have made a brief internet search for the relevant info and instructions but have not been successful so far.