Featured Convertible brooch

I hadn’t looked closely at this brooch until today when I realised it divides into two clips.
I don’t know if the box is contemporary but the brooch looks like new minus one stone.
Would it be 50s?
The slide clasp is only marked 8.
Thankyou

 

I own a similar one that I purchased in the Czech Republic and that I assume is Czech in origin. Not sure about age though.

 

I think they are called duette brooch..
https://www.google.com/search?q=duette brooch&tbm=isch

 

Missed off two photos!

 

Thankyou.
Some of those are 30s so maybe my guess is out!
Looks like Ciro did make them so the box could be right too.

 

There's writing on the back of the brooch part, but I can't read it. The famous costume maker of duette brooches was Coro, but this isn't theirs.

 

Duette is a very specific patent, French originally, from memory. That clasp isn't typical of Coro or the other makers I've had.

 

Well spotted. I saw that and forgot to include the information that it says PATAPPLdFOR which presumably is patent applied for.
However when checking it out with my loupe it also says CP in a box and England on each clip. You can see it top left of this photo.

 

Brilliant, Thankyou INH, as usual spot on,there it is CP England!. So it is the right box!

 

We have a winner!

 

Nice!

 

Interesting cross over with Trifari.

 

Some more information.
https://www.trufauxjewels.com/blog/introducing-duette-brooch/