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Hi, there are actually three crosses Saint Andrews for Amsterdam, check your box if you can find a little sword mark. The maker's mark mark you refer to;
LdB3 in rectangle with cut corners for: de
Leeuw
den
Bouter, registered Schoonhoven 1946-1971
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LdB3, Lion Passant II for silver 835 fineness, Minerva head regional assay office letter M for Schoonhoven, year letter h for 1957
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Similar (nearly) box; Sizes; 5.5 cm wide, 4.5 cm tall and 0.8 cm deep.Weight 27 grams. Office mark for (Minerva Head +A) Amsterdam. Fineness 833/1000, Maker's mark; M+C in oval for Th.& P. Moerkerk(Fa. Moerkerk & Co), working from 1923 until 1928 in Haarlem. Date letter P=1925
A Google search:
zilveren doosje met nachtwacht will reveal more.
Peter.