Hi Heidi,

Yes, we are looking at 3 pseudo marks being; pseudo Amsterdam city mark, C pseudo year letter and B pseudo masters’ mark or two double pseudo year letter.
Antique miniatures always have been in high demand and various silversmiths’s supplied the market with copies of original miniatures including the pseudo marks. The law demanded authentic assay & hallmarking in your case being; genuine makers’ mark of; Hendrik Horstmanshof and the sword mark; standard mark of fineness for small objects, struck by the assayer. The pseudo marks could be considered part of the decoration and probably struck by the silversmith or others and perhaps struck after the legal assay.
For hallmarks see:
viewtopic.php?f=5&t=32028Oel.