size of screws holding back plate of Toshiba Satellite

Yeah. Because Toshiba probably only made 400 different iterations of their Satellite laptops over the last 25 years.
 
Solution
My Toshiba Satellite E45-B4100
has lost 3 screws. Two of which hold the battery in place! It fell out and hit the ground today. Wasn't sure if it was just me or Toshiba's fault. Well, I also kept my old Toshiba laptop which was also missing three screws in the back! So my Satellite C55Dt-A5106 is now down six screws! They fit in my new-ish laptop! It's only 3 or four years old. And I keep it in my backpack using it multiple times a day so I guess that's enough to have them losten up. As for the screw size I couldn't tell ya. I'd just recommend tightening them all periodically!