Dear Don, Unica about 1961 onwards were the first nylon/plastic saddle to my knowledge. Famous riders who used them first were Adorni, Balmamion, Bitossi and Nencini. Dunlop made a sort of rubber come plastic type years before these I think were called something like Duralastic. One of the many Brits on the list should be able to come up with the correct name. Unica and cheapo Brooks B18's are wonderful saddles. Kindest regards Frank.
Frank Cohen Hoxton UK