Lawrance Series 20-A D2 2 cylinder OHV. APU aka putt putt aircraft generator. Magneto ignition with shielded wiring, Bendix carb and shrouded exhaust.
I have never tried to start it but it turns freely with compression. What you see in the photos of the actual APU is what you get. Overall pretty decent condition but there is a bit of a crimp or ding in the exhaust pipe tip and shroud exit - readily repairable. Please see the photos to judge condition for yourself. See the page I included from Aircraft Engines of the World for specs and description.
The item "WW2 US Army Airforce B17 B24 APU Putt Putt Generator Lawrance A20 D2 2Cyl OHV" is in sale since Thursday, March 30, 2017. This item is in the category "eBay Motors\Parts & Accessories\Aviation Parts & Accessories\Engines\Engine Components". The seller is "fine-junque" and is located in Cave Creek, Arizona. This item can be shipped to United States.