Marilyn’s Coat   To look less like a gypsy, the advice has been given to wear other than lace-up shoes and to ditch the handbag. Have you brown shoes? A brown handbag to match?   The handbag is chosen for convenience. The shoes for comfortable walking, Don’t look like a bag lady was the thought behind the sisterly rebuke.   True, the coat’s an artwork; is enormous, glamorous, creatively patch-worked with tassels, gilt and random buttons, scattered.   It has been immortalised by its portrait displayed on the National Gallery’s website in one year of Portia Geech’s famous exhibition; with…