Arnold Wagner's original 1,000cc BMW boxer twin engined Oekomobil which was first ridden on Swiss roads circa 1982.
The first K100-engined 4 cylinder machine, built in 1985, can be seen here: http://www.bikeweb.com/node/1806 on the Ecomobile and Monotracer page here: http://www.bikeweb.com/image/tid/104
PNB