OK, I was able to measure the stone in the setting.  It measures 14.12 mm across and 8.6 mm down.  I looked it up for conversion to carats and it says 10 carats.  That is a big stone!!!  The stone is prong set.  It's a beauty!!  I believe the small ones around the stone are Marcasite.  Open back.  Nice heavy ring so there is lots of Silver.  It is tested positive for Sterling and marked 925.  The stone on the Presidium tests as Quartz.  I don't know why??  Size 5 1/2.

Any shipping within the US will be via USPS Ground Advantage with insurance.  I will be happy to combine shipping if you purchase more than one order; however, it is best to drop your choices into your cart and hit continue shopping.  Contact me then for a revised invoice.  I am also able to take a list of what you want and make a special Ebay listing for you to combine shipping.  That way you only pay for the weight of the package and not what Ebay would consider for shipping.

Thank you for looking.