Hi Amena,
Your second post was very helpful; well, both nautilus shells look new (I mean, the shell itself).Compare with many nautilus conchiglia offered online.
Shells of whatever kind change their appearance and they age, being exposed to air and light, acquiring yellowish tint. Moreover. they show signs of wear often similar to so called age cracks seen in very old pottery (majolica).
The same process of natural ``ageing`` can be observed in ivory and tortoiseshell.
This is my Georgian cowry shell snuff box to see what happens to the shell after 200 years.
![Image](https://abload.de/img/ydh5flakfqrfdfw.2371xkwk0c.jpg)
Besides, filigree work in second example is overall esthetically very poor mounting particularly with this coral rose.
I suspect the base (foot) of the first example is taken from elsewhere and married to create the mounting of the cup, because it`s embossed and much better than the rest of the mounting.
Those facts really indicate fantasy marks I have never seen, either.
Reviewing all seller`s items is very helpful because they are often betrayed by several identical or similar pieces supposedly centuries old, which is statistically impossible.
Regards