The other Magnin"" made it big and sold out to a conglomerate years back, while ex-proprietor Cyril Magnin went on to become (among other things) San Francisco's official greeter. But the interest of has story hinges, still, on that once-notorious rivalry in American-Jewish retailing. First there was I. Magnin, founded by Cyril's formidable grandmother Mary Ann (but named, in accordance with 1870s mores, after her offstage Marxist husband Isaac). When she passed over second son Joseph for promotion, he got out--to start Joseph Magnin in direct competition with the swank, well-established family firm. Growing up in the store (all the Magnin young did menial labor), going East on buying trips from age 20, facing rebuffs from I. Magnin suppliers, Cyril was convinced JM would never be anything but ""the second-rate Magnin"" unless it changed course--and, in the war years, went after ""all those free-spending young people coming up."" With ""dire warnings,"" his father turned over the store to him; he had meanwhile married successful young N.Y. designer Anna Smithline (older sister of Adele Simpson), who ""provided the class for the store""--and had an in with manufacturers; and JM took off, youth-ward. Much of the credit Cyril gives to his ""kiddie corps"" of art and advertising talent--young women (mostly) who walked in off the street and convinced him JM needed a new image. He ticks off a list of Fasts: ""the preferred customer"" (granted unlimited credit), the ""Wolves' Den"" for gift-seeking men, the boutique concept, ""image"" advertising, designer Christmas boxes. And he has testimonials and awards to prove it. But when JM had umpteen branches (and no place else to go without more capital), when Cyril decided that ""the heyday of women's apparel was over"" (what with so much else to spend money on), the firm was sold to a conglomerate--with the usual dire, disillusioning results. Cyril was by now a big Democratic-Party contributor (LBJ also called on him to spiff up Lynda Bird and Luci Baines); he became embroiled, as Port Commissioner, in the aborted S.F. harbor redevelopment; and since 1963 he's been the city's first, self-nominated, striped-pants chief of protocol. Quite a way, in the American way, from Seventh Avenue snubs--and though there's overmuch ado about ""the Magnin magnetism,"" collaborator Robins deserves credit for not toning Cyril down too much either.