I used sew-on snaps ("female" half only, as the welded in posts act as the "male" half). Used an arc of thicker leather, between lining and bag, which I sewed the sew-on snaps to:
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This is not the first sporran I've made, but the first for one of these brass cantles. With the sew-on snaps, one could make any number of different bags, to use with the brass cantle.