Thanks for the replies, and the welcome.
As I mentioned, I was hoping to avoid anything controversial!
My question is based on the fact that the vast majority of dress sporrans on sale in Scotland (in my experience) these days are seal skin, and these are sold as being the traditional choice for formal wear. After browsing the vintage photos on here it seems there are plenty examples from the 50's onwards and perhaps some from earlier.
I am interested to know when seal skin became the common choice for dress wear sporrans, or if there was ever such a thing!