Now that is interesting!.
It looks pretty much right, there's no real signs of it being got at.
Being a type 5 the handle/tote would've rested on a cast seat.
But with the way the body of the plane has been made the seat and the handle would just hang out the back with no support.
I spend a lot of time looking at Siegley's and I've not seen that before.
I'd suggest if you restore the plane take your time, do your research and put it back together as original as possible.
She's a little beaut!.
Let me know if there's anymore info I can help with.