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there are a number of Italian producers who place the serial on the side of the seat tube just below the seat lug
some place it on the drive side and some on the non-drive side
Cesare Rizzato (Atala, Atlantica, Corso, Lygie, Maino & others) places it on the drive side also but in a rising rather than descending order
here are two examples on Rizzato built Maino badged cycles -
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