AMERIKANER A*D GOLD FILLED BROOCH, Andreas Daub

Flea market find. I think I paid more than usual for this one. The stones look like garnets.
Marked AMERIKANER A*D.
I am a little bit confused - some sources say Amerikaner A*D was for Andreas Daub, but some say this A*D means "Auch" (attention) "Double" (doo blay). But since mark A*D belongs to Andreas Daub company, I will stay with this one.

P.S.
If the AD mark is without star, maybe this means the gold filled jewelry, double? Like it is pictured on my other german necklace :
http://www.collectorsweekly.com/stories/197045-necklace-marked-k-and-b-ad?in=705

P.P.S. davyd286 suggested to contact Andreas Daub for their verification as to clarify the A*D vs AD difference.
They kindly answered:
"We confirm that the A*D as it is shown on the brooch is our official mark and that we also – still today – stamp Amerikaner in order to describe our high quality Doublé quality.
We haven’t got the picture in our current picture books anymore and therefore cannot recognize the style 100% as ours or even date it. We are sorry for that. As the mark however is 100% ours we confirm that this piece is most probably from our production.
In respect to the “Kb” picture I think that it could be K&L - Kordes & Lichtenfels (Korli), another well-known old German jewellery manufacturer.
Enjoy your jewelry !"
Link to Kordes & Lichtenfels necklace that I sent them as well: http://www.collectorsweekly.com/stories/201021-kordes-and-lichtenfels-necklace

From internet:
This company was owned and jewelry designed by Andreas Daubs in Phorzhiem Germany from 1896 to present. It is still run by family members. The word "Amerikaner" is the same as "double" and this was a process of double plating an item which was created during the Austrian Empire period (prior to 1865) and assured a lifetime glow. It was used because pure gold was becoming scarce due to fine metals needed for the war efforts throughout Europe. Around the time of the Civil War an American technique was created which was the same as the "doo blay" of Europe and it was then duplicated in Europe.
Also:
The German and Austrian jewelry which utilized this technique had it stamped with the name "Amerikaner" and the "A*D" represented "Auch" (attention) "Double" (doo blay). This was to demonstrate that the item was a patented mark "attention" usually referred to the command for no duplication. Items created with this process basically were of 9kt or 333 to 375/1000 gold. They could be higher. Base material was silver with copper which allowed for the rose gold color. "Double" is an outstanding hallmark along with "Amerikaner" and holds 35/000 micro edition as upheld by the world gold standard. It ceased to be at the beginning of the First World War.