Phi Mu Alpha Sinfonia's has changed little over the years. The current form (illustrated in this graphic) dates from 1910:
Originally (1898), only the letter "S" was found in the triangle -- the Greek Letters were added in 1904 or 1906. For a short period around that same time, a point-down triangle was used.
And unlike many other GLO's, the manner in which the pin is jeweled is not a matter of personal preference -- the placement of the garnets and pearls is part of the official design.