Thank-you for posting. At least now we know that some of the models were made in Japan, as previously suspected. Too bad there's no photo the serial number. The subject bicycle appears to have a Shimano Selecta B crankset mated with Shimano Altus LT derailleurs. Both were introduced for the 1979 model year and the derailleurs survived into at least 1984, so it could still fit into that known 1982-1984 timeframe for Manta. Or maybe it could push the introduction date back a bit.