Just offering some friendly-intended educational information here, because the info is important for correctly identifying this and other buttons.
Actually, that is not a crown. It is what is called a Coronet. Notice that it has several "knobs" spread out in an arch at its top.
Crowns are worn by Royalty. Coronets are worn by the Nobility... such as a Duke, a Baron, a Count, etc. Each of those ranks is represented by the number of "knobs" shown on the coronet. (For example... IF my memory is correct, 5 knobs means a Duke.... but I might be miss-remembering.)
Also... this button SEEMS (I can't tell for sure) to have what button-collectors call a "self-shank back"... on which, the back itself forms the tunnel for the thread to pass through, instead of having a separately-made-and-applied wire loop. We need a sideview photo, to show us the actual shape of this button's shank.
One of the photos attached below shows a Coronet on a "Livery" button. The other photo shows one version of "self-shank back" -- all of which are from the 20th-Century.