Various styles of formal dress seem to exercise the imagination of many contributors here, the reason for which intrigues me but may perhaps lie in a latent desire to re-create a long-forgotten age, redolent with Kings, Queens and all the Cinderella trappings supposedly associated with them. Functions such as "Caledonian Ball's" are largely anachronisms in this day and age and that illustrated guide to forms of Court dress belong to a bygone era which ceased along with debutantes 50-odd years ago. It is certainly no longer appropriate should any member here receive an invitation from Her Majesty. As an instance of this I know from personal experience that guests from Scotland at one fairly recent Royal event, the marriage of Prince Charles to Camilla Parker-Bowles, were wearing PC's, white hose etc. to the daytime event so to attempt to infer that such inviolable rules still exist is misleading to say the least. It also begs the question raised in another discussion about the propriety of wearing such dress in the daytime.
I do agree, however, that there still exist such dinosaurs as "Caledonian Balls" which are the last vestiges of an otherwise extinct society and which exist principally to offer attendees the opportunity to dress up in a way they could not otherwise, and really, to paraphrase Groucho Marks "I wouldn't want to be in any Club that would have them as members".