I'll look it's probably on the inside and I'm not sure how to open the darn thing...I'm listing another one soon! I'm guessing you may know how to open it??
It's a Post-War A2B model. They were made from 1945 - 1950. It was advertised as an amateur or college student camera.
Remove the Back Cover by pressing the Lock Clip. While pressing, either pull on the leather tab on the Lock Catch or pry the Back Cover off with your fingers. If you have difficulty removing the Back Cover, you can pry the Lock Catch with a flat-head screwdriver or butter knife. The lock clip is that thing on the left side that you can see a part of on the back in your 4th picture. Yup serial number etc is on the back cover when you get it off.