According to J. Charles Thompson in 'So You're Going To Wear The Kilt',

"For evening wear, the sporran must be fur and silver mounted. This is not going to look well with a sports jacket or even more informal outfits."

"The only sporran that will serve for all occasions is the fur sporran with the animal's head made into the flap that closes it."

"Plain leather for daywear."

And according to Thomas Gordon Mungall III in 'Wearing Highland Attire',

"The type of sporran selected should be appropriate for the occasion. The silver-mounted purse sporran should be reserved for the more formal occasions. Frequently, I have seen dress sporrans worn with daywear, which should not be done. Plain leather or animal masked sporrans are appropriate for daywear and, interestingly enough, the animal masked sporran is one of the few all-purpose sporrans that can be worn with the most formal dress or the most informal wear."

Does this mean that a plain leather sporran should only be worn during the daytime and only a fur silver cantle sporran should be worn in the evening,

or,

simply that the formality should dictate the choice of sporran, whether day or night?

Or am I just being anal...

Larry