along with the threeoldagfa cameras from ebay i also got two old agfa flashes, recently.
this is one of them: an “agfatronic 261b” flash. it puts out a pretty solid amount of light, presumably it’s gn 26 @iso100. there’s nothing to adjust, as far as i can tell (neither the focus of the output nor the amount of output)
however, sadly i couldn’t get it to trigger entirely reliably with my phottix remote trigger. it seems that using rechargeable batteries works less well than when using disposable 1.5v batteries in the trigger.
as with many older flashes, this one also has a trigger voltage well over the 6V that canon recommends, or the 24V that some ISO standard recommends. so it’s not a good idea to attach it to any modern digital camera - the flash might fry them.