The water-drop test
Put a single drop of water on a hidden area — the back of the frame, under a cushion, the inside of an arm. If it beads and sits on the surface, the leather is pigmented and carries a protective topcoat. If it darkens the leather and absorbs within a few seconds, it is aniline. If it absorbs slowly and partially, it is semi-aniline. Wipe it off either way. That ten-second test determines the entire cleaning approach.