“70's made in Turkey ... 220v european voltage. ... Only very old people knows that brand "Booster" ”Â
The rough sand-cast aluminium enclosure looks like a reference to early Roland-Boss enclosures, it does serve only little for knob-protection, though.
It has a quite low output, so “Booster” does not seem to be a function of the device, but maybe the brand name, indeed. Furthermore it offers a moderate phaser and sort of a flanger at the extreme settings of the speed knob.
The PCB looks quite identical to an early Electro-Harmonics - Bad Stone phaser (the greenish, perhaps even older PCB is an example), so it might very well be a one-off rehouse with modifications.
Given it’s age there might be a connection to the Turkish Rock scene in the 70s?
cred: reverb.com/Mustafa Sahin, home-wrecker.com/badstone.html