This uniform is significant for several reasons. Up until 1914 Swiss Guard uniforms evolved with each pontificate. Primarily the piping on the jacket bearing the coat of arms of the reigning pope is what changed.
After the death of St. Pius X the uniforms became reminiscent of the original ones from the 16th century. In Rome today you see the more traditional uniform.
However, this one dating from the pontificate of St. Pius X is unlike the present uniforms. It is in perfect shape with a jacket and pants. Only the stockings are missing.
Father Kunst has visited the Swiss Guard armory and they have noted that they do not own a uniform from this time period and are seeking one.