It is a civilian blazer/sports-coat button, from the 2nd half of the 20th Century, showing the emblem of the (Scottish) Royal Black Heath Golf Club. It shows two crossed golf-clubs at the center, a golf caddy at left, the thistle-flower of Scotland at right, two golf-balls below, topped by the Royal Crown of the British Isles. Supposedly, the "letters" around the button's edge are Scottish Gaelic runes/letters.
Your button is not really from the Royal Black Heath club, the emblem has been pirated, or perhaps was never Trademarked. Several slight variations have been posted many times over the years here in the What-Is-It forum. See the variations in the photos below. Theoretically, with the Golfing Club emblem it would be used mostly on golf-jackets, but those buttons turn up far away from golf courses.
I should mention, two of the varieties below show the "black enamel finish" which is commonly applied to civilian brass Fashion buttons to highlight the emblem.