From the photo, your fork stem looks to be the same as that on the 'Druid' forks that I have on my sprinter. Unfortunately, from the photo, it is not easy to make out whether the cross pivot is in line with, or fore or aft of the centre column. On mine, it is in line and the bottom of the stem has a machined face for the friction disc. This face also has 2 locating pegs - in line with the cross tube - to locate the bottom damper plate. The order of assembly (from the centre column, down) is: 1 friction plate, 1 steel plate that anchors to the frame (shown in photo), a second friction disc, a second steel plate (with 2 holes for locating pegs and a tongue to locate on the centre plug), and a 'star' spring. All this is mounted on a headed centre plug which is a sliding fit in the bottom of the column. Now this plug has to have a slot machined through it to accommodate the bottom fork pivot pin, and a keyway for the tongue on the bottom plate - and the top is threaded for a stud to connect it to the damper knob. The biggest drawback with this setup is that the forks have to be dismantled to remove the bottom pivot if the damper needs any attention.
From your photo, it looks as if the centre plug my have been modified to have a removable nut instead of the head - in which case, it would then be possible to dismantle the damper without pulling the forks apart.
Hope this makes some sense!! - get back to me if you need any more details.