Can anyone identify these marks on art nouveau flatware?

I would be very grateful for any ideas on these marks, found on the reverse of six teaspoons and five knives, all featuring an art nouveau design. I have spent hours researching these but so far drawn a total blank. Appears to be a number ‘6’ (or ‘9’ and some sort of winged creature.

They could of course be good quality silver plate, but have several deep marks on them and after careful polishing show no signs of any base alloy. The items were bought here in the UK, but a friend thought they may be continental. Many thanks if you are able to help solve the mystery.
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