Hello, Eclipse. Welcome to the TreasureNet forum.
Size is often important for getting accurate identification of a button, but you did not tell us the button's size. Also, the location where the button was found is very important.
http://forum.treasurenet.com/index.php?topic=259110.0
Your button is a nearly flat one-piece brass button with a "die-stamped" emblem. Most of that kind were manufactured in the 1800s (mainly between 1800 and 1850). So, your button is most probably from sometime in the 1800s.
Because you did not tell us where the button was found, I looked for clues. I see the flag of Belarus with your name, so I assume that is where you live, and also is where the button was found.
In Europe, a button showing a crown above an eagle usually is an Imperial or Royal Army button. So, if the button was found in Belarus, it is probably a Russian Imperial Army button ...meaning, the Czar's (or Czarina's) Army.