If they'd known the maker, or had a reliable attribution, the Newell-Smiths, owners of the Tadema Gallery, surely would have noted it. Falk's 'Jugendstil-Schmuck/Art Nouveau Jewellery from Pforzheim' (2009) features a large number of pieces from their stock - it's a luscious book, my copy unfortunately packed away at the moment, but will see if I can dig it out in the next few days, just on the off chance your piece might be there... ~Cheryl
That would be in my hoard (I'm not even bothering to call it a collection any more) so fast.... Plique a jour is seriously cool.
So nice of you to offer ... THANK YOU! But don't feel that you need to do this any time soon ... whenever you get around to it would be fine with me - the pendant won't be going anywhere (other than dangling from my neck), anytime soon.