Thank for for making and posting photos of the button after thorough cleaning. The new photos confirm it has actual gold plating ("gilt"), not a modernday "golden finish," nor paint. Also, the animal's head on it now looks more like a Bobcat than a lion (which has round-topped ears, unlike your big-cat's ears). That, and the gilt, and the well-detailed fancy background on your button make me think it is a mid-1800s to late-1800s "Sportsman's button." At that time, the term Sportsman tended to mean a hunter, rather than a Sports player. Sportsman's buttons from that era typically show a hunter's-quarry animal (regardless of whether it was hunted for food or just to be a trophy), or hunting-dogs, related scenes, etc.