Looking for info about this makers mark. Looks like around 1850 work. Is J with kind of double F in circle. Found maker using JFF in Shefield in 1856 but the mark was different.
Not Ireland or Sheffield. If the silver standard mark is 900 that should cut down the list of countries to consider. There is a list of countries and silver srandards at https://www.925-1000.com/a_Standards.html