The sterling stamping started sometime around 1870s, so that provides a cut off date. The style of the monogram and design points more towards early/mid 1900s in my opinion. Maybe someone else here knows more and can narrow it down better.
Some had the Hickok mark, and some did not. Some were marked Hickok, and not STERLING too.That might actually help date it, if you do a little more sleuthing work on Hickok.