I tried to read what the stamp said, and it looked to me like there was an F after 14KG.
I didn't /don't see 585-- and you didn't mention it in your first post. We aren't mind readers; it helps if people tell us what they know about a piece before asking us for our opinions ;) .
Since it's gold...
The clasp appears to be gold filled from the stamp on it.
The pearls-- my first impression was imitation. Or maybe just really poor quality, whatever they are. Sorry.
Please note that I edited my first reply as I made a mistake the first time I looked at your photos. On looking again I see that only one of the necklaces is graduated.
Welcome to Pearl Guide!
You have 1 graduated knotted strand of vintage akoya pearls with a 10K gold fish hook clasp; the other is not graduated and not knotted, but also has a gold clasp.
I think the unknotted strand is also akoya --are they all round? The photo makes some of them look a bit...
These are called tokki pearls. SSEF magazine (Swiss Gemmological Society) used to have a good article on how these form but the article seems to be gone.
Two pearls join to form one pearl; the smaller sometimes forms from a bit of broken off mantle tissue that forms a pearl sac and secretes...
I think the OP was wondering where the bit of pearl dust on the black mat came from. Marianne explained that it could be dust from the drill hole, left over after drilling.
You may wish to read this detailed and highy informative series on mabe and blister pearls, written by @CortezPearls.
It starts here:
https://www.pearl-guide.com/threads/i-introduction-to-blister-and-mabe-pearls-ultimate-guide.454956/