Sort of XLR (Cannon) connector with 4 pins
pin 1 +12C DC pin 2 Nothing pin 3 +12V DC pin 4 GND
Thomann.de, part (artikel) 180235
This lamp has the following pinout :
pin 3 GND pin 4 +12V DC
On the thomann.de site, in the description of the part, you find the opposite pinning. I don't know if the site is wrong or if I get a bad part from them. In any case, it is very easy to adapt it to anything because you can easily open the cover and solder the wires as you need.
In order to use this lamp on a Soundcraft GB4, you have to modify it: