Hi SilverK,
Herewith an other example of this unknown retailers or maker’s mark (?);
G Sphinx /Lion G, herewith double struck on a loderein ( lodderein or odelarein) box , with the silversmiths mark;
G. over 28 for Dirk Hendrik Greup Sr, registered in Schoonhoven from 1837-1864.


Please note; Dirk Hendrik Greup’s mark has been partly struck over the assay office mark and this could indicate he struck his mark after the box has been assayed and I have seen his maker's mark struck over an other maker's mark.


Date letter T for the year 1853, and the office mark, Minerva Head regional assay office letter M for Schoonhoven

Your image:
Yes, I agree the date letter A for the year 1835, The office mark, Minerva head has the regional assay office letter A in its helmet for assay office Amsterdam.
The maker's mark rotated:
Maker's mark (worn); NK under a fish (pointing left or right) for; Jacob Nicolaas Kramer, registered in Amsterdam 1826/1853 with a total of eight variations of this maker's mark's see:


Unfortunately the Sphinx mark is still unknown but we are still working on it!
Best,
Oel