People often get confused about frame material, my guess is that he was told about it being a steel alloy (in the 1960s chromoly was probably not a term people used), and that is had a high manganese content like in a carbon-manganese steel.
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1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear