What is this erased mark on this bedouin jewelery?

[Joerg]

I have this bedouin jewelery 30 years now. It is time to find out some information on it. Can you give me some basic information about it? How old is it? Where is it from? I think it consist of older parts, the band, and newer additions, the chain and the side pieces. Do you agree? And foremost, what is this scrached mark on the back? Any ideas?
I bought it in northern Saudi Arabia. The seller said it is from Yemen.
Thank you, Jörg