Pajamas were cool in the early ’70s—and not just for nighttime. Spring collections showed evening dress that was a cross between daywear and bedclothes. But how do you make loose knits and kimono shapes suitable for black tie? Add Van Cleef & Arpels. Take this navy ensemble modeled by Beverly Johnson in Vogue in February 1974: The jeweler’s diamond Rose de Noël clip secures her jersey cardigan over her slip dress.Van Cleef & Arpels created the Rose de Noël in 1968 after the civil unrest that May in France. “Before that, the elegant upper-class French woman was wearing jew