Thank you for that careful and inciteful analysis. I agree that the tassle cords appear newer. Looking closely they appear to be all cotton and not a synthetic as you'd likely find today. I can't see how the badge is attached as nothing shows on the back, so if it is not original someone had to have torn the sporran apart to attach it. It is a flawed brass stamping however. so definitely mass produced.
The fur is quite soft, more like fox than deer (at least the white tailed deer in north America, which have quite coarse fur). Another curious feature is a series of pin holes around the cantle, which appear to have been made from the back but can also be seen on the front as raised spots.
BTW, it was quite inexpensive, and the shopkeeper knew next to nothing about it. He was unfamiliar with the work "sporran". But he did sell it with the ermine tail pin as if they went together.