Reader Jeff has recently become the lucky owner of a 1960 Royal Enfield Interceptor VAX "S". In 1960 Royal Enfield launched a line of bikes which are a highly tuned version of the 692cc Constellation, and sold them only in the US. The Constllation was shipping with "VA" engine numbers and these ones became "VAX" for experimental. They were the first wave of what would later become the 750cc Interceptor. According to Wikipedia: "They had twin carburetors (except some early bikes), a factory lightened and balanced crankshaft, hot "R" cams, Lucas racing magneto with manual advance and a few other weight saving modifications compared to other Royal Enfield models. There was also an Interceptor "S" (Sports) model with "highway trim" -- quick detachable(QD) lights etc, offered when Enfield failed to sell sufficient quantities of bikes in the standard scrambler trim. 163 bikes are made as per the Redditch factory despatch ledgers held by the Royal Enfield Owners Club in UK. The very first bikes left the factory in December,1959 and the last ones were despatched in July,1961. The engines in the highly tuned form demanded proper maintenance more than similar 692cc models and many ended with catastrophic damages to the bottom end. Only a handful of these bikes survived which makes them one of rarest post-war Royal Enfield models". Other sources say there were 211 bikes shipped. However, Jeff contactedd the Royal Enfield Owners Club and they estimate the number between 158-170. Apparently they were shipped as scramblers, to cater to the growing US motocross scene of the 1960's and the "S" model was a street conversion carried out by the California dealer Cooper motors. So this is a very rare motorcycle. More pictures here.