This pin-brooch is dated to before 1921 based on the type of clasp on the back.  This brooch does not have any marks that I saw and I acid tested the metal.  It held at 10K..possibly 12k.  It has a small but pretty opal in the center.  The opal is 4.6 mm wide.  The piece weighs a total of 3.4 grams.  This brooch also does not respond to a magnet.
I know it is hard to decide to buy jewelry on the net.  I promise that I will try my best to accurately describe the pieces that I put up.  I also guarantee the purchase.  Once the item is paid, shipped and delivered, if you are not happy with the item, you only need to contact me.  If I state that a piece is sterling or 14K or …it is because it is marked.  If there is no mark, I will acid test it and tell you that it was acid tested.  I use a “Jeweler’s Delux Edition Diamond Analyzer” to check all clear stones.   Please note that I am not a jeweler.
I am willing to combine items for shipment to potentially reduce shipping costs.  I can
only do this
if the items have not been paid.  Once you win the first bid, please send me a message to let me know that you are bidding on a second item.  Once the additional item(s) have closed, I will send an invoice with shipping adjusted and you will need to pay from that invoice.