How does the seat lock work?

[drrummel]

I am trying to repair damage from a previous owner. The seat lock has a tab that goes into a hole in the frame of the bike. I see no lever in that hole. When I move the lever behind that hole towards the tail light there's movement but I don't see what would latch an unlatch the seat.
The tab on the lock goes into the little square hole.

[GrumpyUnk]

In the last pic, look closely at the top edge of the hole where the top end of the spring is hanging onto the bent up tab. Looks to me as if there's something that has been removed. There are some 'remains' along the top edge of the hole.
To know, I'd have to see the underside of the plate shown in the pics.

In the top pic, two things look as if they show evidence of being touched regularly.
The tab that hangs down in front of the spring looks as if it has been pushed/pushing on something regularly.
The movable 'latch' that sits in the indent at the closest edge looks as if it has been touching something also. That looks like a 'striker plate' that is poked at by the seat moving, and things like that generally move as the pin/arm pushes, and finally snap into a 'latched' position. In this case it would likely be 'caught/trapped' by something under the latch plate(with the 4 bolt holes to keep it in position.)
IOW, I think the latch mechanism may have been gutted of necessary parts and will not work without replacement.
tom