Thank you to everyone for helping me to figure this mystery out.
I tried the water test, but no ink showed, just a little dust! This version has three drawers and no paper tray.
The drawers are labeled 9-776, and 7-776. Interesting trying to get the drawers out, you have to release a spring by poking a small screwdriver in a hole in the back bottom of the drawer. It's been fun exploring it!
Now I have another project for this summer!