I can help you on this one.
The scarab is not turquoise, it is either lapis lazuli (stone) or it is faience (glazed ceramic paste) both are traditional materials for these in Egypt. You are right, the setting it is in looks old. Prior to Egyptian independence, it was legal to take ancient antiquities out of Egypt, so there are lots that came over to the US and Europe during the late 1800's and through the first part of the century. Graves were desecrated and ancient artifacts were made into tourist jewelry. I have some of these at home too and you can get them on Ebay quite easily. I recognize a couple of the heiroglyphs. That first one with vertical lines sitting on horizontal lines I believe is a Senet board. Senet was an ancient Egyptian board game, that was kind of like chess or checkers. The one on the lower right is the feather of Ma'at, or the feather of truth. The heart of a deceased person was weighed against the feather of truth. A person whose heart was "light" or free of heavy burdens of guilt, would move on to the afterlife. A person whose heart was burdened by guilt and bad deeds was devoured by a creature (kind of a monster made of several animals)
Now the big question- Is it ancient or is it a modern tourist item. The setting makes me think there is a good chance this could be real, because they have not done that kind of setting on tourist pieces in many, many years and I think there is a chance that yours is an ancient scarab that was mounted in the twenties or thereabouts. The other thing that this has going for it is that I can recognize a couple of the heiroglyphs. I cannot read them though, I do not have that level of expertise. What really intrigues me is that there are some under the silver mounting, which to me says that it was added later, unlike a piece made to go into a mounting.
The hard part about antiquities is that they are frequently faked. Sometimes they are easy to spot and other times they are not. Yours has all the things above telling me that it is authentic. Not terribly valuable, but very cool and very ancient nonetheless. The other thing to consider is that back in the time when that mounting was put on, it was legal to get these. There would not have been a big market for fakes like this, which would not have brought a lot of cash.
I would contact Lisa Swappach-Shirriff, who is the curator of the Rosicrucian Egyptian Museum in San Jose, CA. She is a very nice lady, I have met her. See if you can show her your photos. Best of luck and congrats on a neat find!
http://www.rosicrucianegyptianmuseum.org/contact
