Info needed on old cameos

I bought an auction lot and these cameos were part of it. They're nice cameos but I don't know how to determine their age and I can't read the marks on them.

Any help is greatly appreciated.

 

With those upturned noses I think they are 20th century. The first 2 mounts have tube hinges and rollover clasps, so I would date them to the first quarter of the 20th century. The 3rd one in the 830 silver mount has a newer hinge than the others and a rollover clasp. Those plus the marcasites look like 1930s-40s to me. I'm not sure on the material for the cameo on that one, the flat back makes me wonder if it is something other than shell?

That is all just my opinion, wait for @Bronwen to stop by

 

The first one is pretty great IMO. That hair!

 

I didn't think they were terribly old. Especially the 3rd with the prong setting.

 

All three are helmet shell, I would put them to the 30s - 40s, Italian settings. Last one is goddess Diana. Mark on the first one is likely to be an incomplete 800. Very pretty.

 

@Bronwen I see "G &" on the first pin. Is that the start of an old jewelry company's mark?

 

Squinted at it but couldn't turn it into a G. I can see the upper part of an 8. I've never seen a maker's mark on the pin stem, but the metal fineness is stamped there all the time, & 800 is the fineness I see the most.