Thanks Daniel, I had to give up on trying to get that apart. I did eventually after a few hours get whatever was inside out and now the piston isn't binding.
The two little screw holes that hold the steam chest down to the pressed metal base were stripped. That wasn't a lot of fun re-tapping them to the next metric larger size, but its a job all done now and the little fleischmann aggregate is now put back together and is finally a very nice little runner.