There is a discrepancy between Birmingham date letter O (Antique Capital letter »O« in vertical rectangle cartouche with clipped edges) = 1863, and a possible maker's mark »S.B« (in horizontal rectangle cartouche with clipped edges) = 1883 registered for »Stainton Bros.«
This kind of time gaps has ever to be hold in mind; before any attempts of attribution would be made!
An other thing is: For »Stainton Bros.« I haven't found until yet any description of their product range = indeed also very important!
Very seldom you could get from a tree of cerise’s, plums.
So actually it could be stated only: Birmingham 1863/64 (Birmingham date letters were changed every year, valid from 1 June to 31 May; until 1974 - from 1 January 1975 on, all British Assay Offices changed on same date their "Year letter").
Kind regards silverport