Not quite shure..... it was announced as an REX engine, supposedly early 60s...but after some checking seems to be a Peugeot SPX (Polini?Tomahawk?).. year is impossible to find out, they never did an understandable list on fabrication numbers. REX engines was mostly used on driving the front wheel, and yes its a little similar. Would believe from the mid 70s- to 80´. Engine have papers signed by German "traffic dept", thats buildyear -57, 49cc, registred by the engine number..... but it got a 81cc cylinder/head by measuring. In very good shape, some parts was bad/missing, but changed now (ignition,clutchdisc/pads). Found axle/pedalshaft/ drivepulley of an Tomahawk moped, and quite easy conversion... 2 shaftsupports to fit the original bicycle bearings to pedalshaft, and on! The drivepulley have an lock/unlock device for a chainsprocket in the back. kick pedals to start, gas to go! Got decompression valve in the head..if its a peugeot it would be approx 2.5hp as 49cc....what this have?? Dont know....but price was ok! Looks quite "fat" in the frame, but also a little oldstyled, so i could (together with the documentation) proclaim this is an old engine, who could have been on the market in the 50s, as i need,to get this legal used at the roads as a vintage vechile, with no licensing needed!!