Saw this ERZET 640 on a German “Classifieds”. Have never seen it before, but the quite simple/rudimentary design made me buy it since the price was fair. It even came posted with 1/2 tank filled with smelly gasoline. The burner bell holds a loose inner ring and two top plates, which moves freely. Spares hold an extra top plate, filler gasket, some graphite sealing and an additional jet. The regulator moves firmly but free. Figured it must be tight since no leakage was seen during shipment. I then did a quick inspection of pricker and the SRV, put some new fuel in it, and fired it up. It just worked after (a bit of heat under the tank) in a strong steady flame with a nice roar. Actually it produces quite a lot of heat! Kettle test went fine - no soot and fast to make a boil. The stove was made by a German tin toy company HANS RUFF from ZIRNDORF (HRZ) which existed 1928-75. I actually sort of like the simpleness/roughness of the design. Cheers.