Mark 3 seat

I have a new to me Mark 3 that I'm bringing back to life. Over the years I've had '71's ,'72's and '74's so I'm familiar with Commandos. I want to use the standard roadster seat (came with a brand new one) on this bike, but cannot figure out how the locking mechanism works. The bike came completely disassembled as a true basket case, with most of the parts accounted for complete with a working lock and key. The parts book doesn't have a good diagram of the set up, and was hoping that someone could post a close up picture of both the lock and hinge side of the seat.

My Mk2/Mk3 hybrid came with a Mk2 seat, but as the frame is Mk3 I put on a Mk3 seat using the parts books as a guide.
IIRC, it wasn't that difficult.
Anyway, here are some pictures as requested.

From the outside...lock bracket 06-5617 first (against the shock plate) then, RH shock bolt (& washer).


The oval lock spacer fits between the lock bracket and the inner shock plate.


From the inside...'Collar' 06-5626, tab washer 06-5624, nut (lock part), Latch 06-6447, Tab washer 06-5627? (mine doesn't have it and AN doesn't list it), Bolt (lock part). [Edit] Mine doesn't have the 'Collar' 06-5626.

'Locked' position.

'Locked' with tool tray in position.