Yes I think it is the first rear discharge SS,when I called this mower a low arch ,I think it is really a no arch,it's base is flat like the side discharge SS.
I think you have the date right .
"Yes, the ad (below) advertises 10 positions." "Your image shows six?"
Just to explain that ,in the image that shows the height adjuster you can see six positions but behind those serrations are another set of serrations the other set of serrations line up so the adjuster locks in between the outside serrations.
So there are two flat steel brackets both with serrations but in the image you only notice the outside steel bracket , you just can't see the second set of serrations in the image.
