There are four marks on the pin of the brooch.
The third mark is the shape of the dog head mark, the mark for 800 silver from 1867 to 1922. It is so very tiny, it is hard to identify whether the micro tiny city letter is present in it or not. If not, this would date the piece to the period of 1867 to 1872, which seems correct by the style of the piece.
The first mark has two initials ending in S. The first is J or I or L. Considering the number of Josefs and Ludwigs and Johanns working in Vienna at the time... this narrows the extensive list of makers whose last name begin with S, by about half.
The second mark is 800, for 800 silver, and the fourth mark is half on and half off the pin. I cannot make this one out - possibly two cursive Ls within an unusual frame. Any leads on this mark would be warmly welcomed.
1 7/8 inch wide