Welcome to the Forum,
That is a nicely equipped later Model 10ER. Not a lot of them have the Model 4E Jointer like yours. As for the What is this? next to the Lathe Tool Rest assembly it looks like something homemade that someone either used for a special purpose with their Shopsmith or it simply got thrown in with it. You also have the Shaper Fence that is for the Mark 5 but not everyone knows that it was made to work on the Model 10's too. It actually came out before the Mark 5. Below is a PDF of the original Owners Manual for it. Note it is being used on a Model 10ER.
Enjoy your project and keep us posted.
Mark V completely upgraded to Mark 7
Mark V 520
All SPT's & 2 Power Stations
Model 10ER S/N R64000 first one I restored on bench w/ metal ends & retractable casters. Has Speed Changer, Model 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. On bench w/ metal ends & retractable casters.