Sorry, but not that old. The early-20th-Century version of the "self-shank" back on buttons was a simple dome with a hole drilled through it. Your square pressed-&-formed self-shank is approximately 1940s-to-present (still being made and sold today). See photos below, showing Sportscoat buttons currently for sale on Ebay. Note the little triangular tabs under the loop, exactly like your button. Also note the buttons' very wide wide nearly-vertical edge, like yours.