Level(s) of formality

[ThistleDown]

With your stipulation that comment must be of the old-school-correct school of thought, FP: traditional mask sporrans quite acceptable white-tie are fur mammals of the Highlands, such as badger, fox, pine marten, wild cat, seal. I've not seen one myself, but I would think otter would also fall into that category. Most often for white-tie they are silver-mounted, but not always. White tie occasions are rare these days, even in Scotland.