They lived in Prague for many generations, so I know that the mark on the left (in the third photo) is the Czech import mark: the fleur-de-lys with a C above, which was used from 1929-1942. Given the family's departure from Prague before the invasion, that narrows the period in question to 1929-1938, I think, unless the same or a similar import mark was used earlier.
What's really puzzling me is the 800 mark, in a coffin-shaped six-sided lozenge, preceded by what looks like a head facing right. (But maybe it's something else altogether?)
These same two marks also appear on a flatware set. I've included some photos of these items and their marks, as well, so you can see a variety of the stamps. Some are clearer than others, but they are all extremely small. (I don't see a maker's mark anywhere on the tray or the flatware.)
I have searched extensively online, and the only things I've found that are even close to the 800 mark are some Hungarian silver marks.
Many thanks for sharing your expertise!
