Hot-air engine made by Ernst Plank ca 1903. As I got it it had some faults, part of the displacer piston rod was missing and the displacer cylinder was broken, but after a cleanup and gentle repair it is now a runner again.

Before restoration

The engine as I got it. I knew the flywheel connecting rod was missing, but after replacing it still didn't run. When disassembling the displacer cylinder I noted why it didn't run. The rod was all corroded, probably due an electrolythic process between the steel and cupper. After replacing the piston top and rod it now works very well again.