I have just posted my shoot of Guy Webster's 175 Catria MSDS:
Phil Aynsley Photography - 1963 175 Catria MSDS
He has it as a 1956 model but as it carries decals showing victories in 1961 & 62 I'm assuming it a 1963 model. In addition it more "modern" looking than the '56 bikes seen here:
Anyone have some definitive info on Catrias?