Yes, it looks like you've found the scooter base I built Pee Wee's scooter on. The "Mongoose" logo looks familiar.
I'm wrong about the original scooter having a foot brake. The rounded slot cut in the part of the floorboard that rises in the back was to make space for the back wheel. I've attached another photo here of Pee Wee on the scooter where you can see that when you look behind his white shoes.
That photo helped me remember that I built a wider and taller floorboard on the original scooter floorboard and because it was taller in the back I had to cut a space for the back wheel to poke through.
The tall gooseneck stem was fabricated from metal conduit and I fit a full size set of hi-rise bike handle bars on the top by attaching the handle bar stem to the gooseneck with a bolt.