Hi Andy The unit is/was a JJC old smokey. It uses water vapour to simulate smoke. It would work on twin stack, the fan assist is slowed down on my tug so as not to give too much smoke, and has speed control to give less smoke on low throttle
However it appears that JJC have stopped producing any of their range of products. I am led to believe that Jim (the chap that did these units) was a victim of his own success, and has had tostop trading in order to concentrate on his full time job. A pity his sound units were quite good also.
Sorry I can’t be of more help
Cheer Tom