OK, time for wild guesses.
One side has a crowned coat of arms, and the inscription PHILIPPUS (possibly V) D.G.; the "U" is the bottom of that side. The other side (with the cross) says HISPANIARUM REX and has a date. Hmm, "1719" maybe?
PHILIPPUS V HISPANIARUM REX would mean Philip V King of the Spains. So this button may have been made from an 18c Spanish coin ...
Christian