Charlie is correct. It is a Porter fireless cooker. Exact history escapes me right now, but it was built for the US Navy (1942?) and ended up at the Natl Museum of Transport in St. Louis. They wanted to get rid of it. So we got it.
Why?
One of our sister RR's the Chicago Terminal, has a customer with a suitable steam plant to charge up this beast. So, in our "spare time" we get to work on it, with idea of someday sending to Chicago to operate there.
Don't ask how it fits into the overall priority of things....